Risk Factors for Higher Cardiovascular Disease Prevalence in Asian Immigrants in the UK: A Systematic Review

South Asians in the UK mainly originate from India, Pakistan and Bangladesh, and have become the most significant minority, with rapid growth from 3.9% of the UK population in 2001 to at least 6.9% in 2021 (only people originally from India, Pakistan and Bangladesh are included); notably, South Asian ancestry accounts for more than 2 billion people (25%) of the world population.^1,2 This rapidly expanding demographic highlights specific health considerations due to a noticeably higher risk of coronary artery disease (CAD) in this ethnicity.³ In 2022, CAD was responsible for 59,356 deaths (10.3%) of overall mortality in the UK and was the leading cause of death in men and the second leading cause overall.⁴ Based on Office for National Statistics data, the mortality rate due to CAD is significantly higher in people of South Asian ethnicity.⁵ Based on evidence, the risk of CAD is more than twofold in South Asians compared to Caucasians living in the UK, regardless of whether they were born in the UK or not.⁶ Because of this higher risk, South Asian ancestry is now considered a risk factor for CAD, second only to diabetes and more critical than dyslipidaemia, hypertension, smoking and obesity.³ As a result, American and European guidelines have established specific recommendations for this ethnic group. The American Heart Association/American College of Cardiology regard this ethnicity as a risk-enhancing factor, and the Canadian Cardiovascular Society guidelines recommend early screening for dyslipidaemias in this group.^7,8 Additionally, the European Society of Cardiology suggests multiplying the estimated risk of CAD by 1.4 for South Asian individuals, showing specific measures for this ethnicity and underscoring the importance of tailored preventive measures.⁹

Common conventional risk factors for CAD include smoking, diabetes, hypertension, dyslipidaemia, obesity and psychosocial stress.¹⁰ A sedentary lifestyle also increases the risk of cardiovascular disease (CVD), such as CAD, emphasising the importance of physical activity.^11,12 Results from the UK Biobank showed that South Asians have a higher occurrence of diabetes (19.5% versus 5.3%), dyslipidaemia, hypertension and psychosocial stress compared to Caucasians.⁶ While second-generation South Asians are more physically active, research indicates that physical activity levels remain lower among South Asians compared to people of Caucasian British descent.¹³ Studies demonstrate that hypertension, central adiposity and diabetes are identified as the main factors contributing to the disparity in CAD prevalence between South Asians and Caucasians, with diabetes playing a significant role. Still, traditional factors do not entirely account for this difference, leaving unclear the influence of novel risk factors such as genetics.^6,14,15

Rationale and Objectives

There remains uncertainty regarding the increased risk of CVD among South Asians living in the UK. The present study aims to investigate the underlying factors contributing to the elevated risk of CAD among South Asians in the UK compared to the Caucasian population, providing insights that may inform more effective, targeted interventions.

Methods

A thorough literature search was conducted on various search engines, including Embase, PubMed and Ovid MEDLINE, for articles published between January 2009 and February 2024. Keywords used were “United Kingdom”, “England, Britain”, “British”, “Wales”, “Scotland”, “Northern Ireland”, “South Asian”, “Bangladesh”, “India”, “Nepal”, “Pakistan”, “Sri Lanka”, “coronary artery disease”, “coronary”, “ischaemic”, “ischemic”, “arteriosclerosis”, “atherosclerosis”, “artery disease” and “heart disease”.

Inclusion criteria were articles published between 2009 and 2024, articles with no missing data, and original research articles. Articles published before 2009, opinion articles, editorial letters, case reports, case series and secondary research articles were excluded. This systematic review used a population, intervention, comparison, and intervention model:

• Population: South Asian
• Intervention: None
• Comparison: Caucasians
• Outcome: Cardiovascular disease

The initial literature search yielded 381 articles, of which 98 were potentially relevant after excluding duplicates. After screening, 17 papers were included in our research. The PRISMA flow diagram breaks this down further (Figure 1 ). This study was registered with PROSPERO (CRD42024533862). Two reviewers independently extracted risk factors investigated in each study to explain the observed difference in risk of CAD between South Asians and Caucasians. Discrepancies were resolved through mutual consent and input from a third reviewer.

The risk of bias for the included studies was assessed using the Risk Of Bias In Non-randomized Studies of Interventions tool.¹⁶ The risk of bias was low to moderate in the included studies (Figures 2 and 3 ).

Results

Psychosocial Factors

Of the two studies on psychosocial factors, one prospective cohort study using UK Biobank data assessed the association between acculturation and CAD incidence (Supplementary Table 1).^17,18 South Asians were classified into different acculturation groups based on their length of residence in the UK (UK-born South Asians, South Asians born abroad who lived in the UK for >5 years, South Asians born abroad who lived in the UK for ≤5 years), noting that more recent immigrants had a higher risk of CAD, after adjusting for traditional risk factors like age, sex and comorbidities.¹⁷

Williams et al. conducted a cross-sectional study that reported significantly higher psychosocial adversity among UK South Asians compared to UK Caucasians.¹⁸ Stressors like financial difficulty, family conflict, overcrowding, deprivation and discrimination were common in South Asians. These stressors lead to depression, hostility and low social support, which are established factors for CAD. Stressors can trigger the sympathetic nervous system, inducing inflammatory responses, and subsequently affect the endothelium, which leads to atherogenesis (Supplementary Table 1).

Genetics and Family History

Two studies published in 2023 aimed to understand the genetic determinants of excess CAD burden in South Asian populations to improve prediction and enable preventive interventions.^19,20 In Gratton et al., the prevalence of genetic variants causing familial hypercholesterolemia (FH) was similar across the different ancestry groups analysed.¹⁹ Using UK Biobank data, the carrier frequency of FH-causing variants was 1 in 226 (95% CI [1 /419 to 1/155]) in South Asians, and 1 in 288 (95% CI [1 /316 to 1/264]) in Europeans. Similarly, in Huang et al., genes and pathways associated with cardiometabolic traits were shared primarily across ancestrally divergent populations.²⁰ Only an abnormal association with cholesteryl ester transfer protein was reported in individuals of South Asian ancestry, which has been linked to accelerated atherosclerosis.²⁰

In contrast, Wang et al. found markedly stronger associations between family history and clinical CAD in South Asians (OR 1.71; 95% CI [1.21–2.42]; p=0.002) compared to Europeans (OR 1.11; 95% CI [0.78–1.57]; p=0.562), and a similar trend for subclinical CAD, suggesting that early interventions were critical in South Asians with a family history of CAD.²¹

Health Behaviours

In a longitudinal observational study with a 21-year follow-up, Eriksen et al. found that lower adherence to four healthy behaviours (non-smoker, moderate alcohol intake, physically active and frequent fruit and vegetable intake) was associated with increased risk of incident CAD in both Europeans and South Asians in the UK (p<0.05). The proportion of cardiovascular events that could be prevented by eliminating the non-healthy behaviours was higher in South Asians (51–63%) than in Europeans (28–43%).²²

In a 2011 study on the contribution of physical inactivity to excess mortality from CAD, William et al. found that South Asian participants were more likely to be physically inactive than Caucasian participants (47.0% versus 28.1%). In adjusted models, physical inactivity explained more than 20% of the difference in CHD mortality between Indian and Caucasian participants.²³

Cardiovascular Disease and Association with Other Diseases

The included studies consistently showed that morbidity and mortality resulting from CAD were elevated in South Asian-origin populations compared to European-origin populations, and South Asians were more burdened by some key CAD risk factors, including diabetes, hypertension, dyslipidaemia and social deprivation.^24–27 In a population-based cohort study, Almulhem et al. found a higher prevalence of type 2 diabetes (aHR 3.10; 95% CI [2.97–3.23]) and hypertension (aHR 1.34; 95% CI [1.29–1.39]) in Asians compared to Europeans.²⁴ Jones et al. reported that 42.1% of South Asians had diabetes compared to 15.4% of Caucasians.²⁶ However, Almulhem et al. reported heterogeneity across South Asian subgroups, warranting further research with disaggregated data to explore any differences in risk factors. They also emphasised the importance of considering lifestyle factors and genetics that are associated with a higher risk of atherosclerosis.

Tillin et al. suggested that other factors, such as genetics, health behaviours and early life exposures, must be considered, as conventional risk factors accounted for only about one-third of the increased CAD risk in South Asians.²⁷ The authors also recommended further research into risk factors across the life course of migrant cohorts.

The Role of Endotoxin in Cardiovascular Disease

Amidst the significant difference observed in the incidence of CVD in different ethnicities, inflammation plays a vital role in precipitating atherosclerosis under the pathogenic mechanism. A study aimed at finding the relation between circulating endotoxin levels with sex and ethnicity found that women had higher levels than men; in particular, South Asian women had significantly higher levels of endotoxins, high-sensitivity C-reactive protein and cluster of differentiation 14 than Caucasians. Though hyperinsulinaemia and insulin resistance are observed with high lipopolysaccharide, as with South Asians, ironically, Africans who have higher insulin levels than Caucasians do not show an increase in endotoxin levels. However, adverse lipid profiles observed in South Asians are consistent with impaired lipopolysaccharide clearance and higher endotoxin levels.²⁸

The Role of Anaemia in Cardiovascular Disease

A study involving 3,563 patients assessed the risk of CVD burden in anaemic patients, of whom 59% were women, 82% were Caucasians, 13% were South Asians, and 6% were African-Caribbean. The age-adjusted percentage showed that South Asian men (20%) and women (22%) had a significantly greater prevalence of iron deficiency anaemia (IDA) than Caucasians (12.1%, 15.2%) (p<0.001); South Asian women (8.2%) had substantially higher vitamin B₁₂ deficiency, whereas Caucasians (73%) had a considerably higher prevalence of anaemia of chronic disease. The study inferred that South Asian women with vitamin B₁₂ deficiency had a higher prevalence of MI (age-adjusted 4.3% versus 1.0%) and ischaemic heart disease (IHD 26.6% versus 12.4%) compared to Caucasians, whereas women with IDA showed lower prevalence and no cases (MI 2.4 versus 2.3; IHD 0.0 versus 12), respectively. Anaemia of chronic disease implied a significant increase in the risk of IHD and AF in the population. However, anaemia is an essential risk factor in precipitating AF (p<0.001), but no significant difference is found in IHD and MI.²⁹

Atherosclerosis

Despite Indian Asians being at an aggravated risk for CVDs, the conventional risk factors and predictors undermine this diagnosis. Coronary artery calcium (CAC) reflects the burden of atherosclerotic plaque in the vessels, but it is unreliable in diagnosing coronary disease risk. Jain et al. employed myocardial perfusion scintigraphy to assess whether it can identify this excess risk in Indian Asians. Subjects were recruited from the LOLIPOP study, and it was found that Indian Asians had 2 years lower average age and a lower BMI, with a higher prevalence of hypertension, diabetes-elevated HbA_1c, higher statin use and lower smoking rate. The univariate analysis indicated that age, higher CAC, and diabetes increased the odds of MI, whereas the multivariate regression model with these predictors produced similar results. Univariable ordinal regression analysis showed that hypertension (HTN) and a history of use of statins were also associated with increased risk for MI. However, ethnicity was unrelated to the risk in both analyses (OR 0.9 and 1.08, respectively).³⁰

In contrast, Indian Asians and Caucasians share a similar risk of subclinical atherosclerosis using CT, despite the former group having a greater than 50% risk. Addressing the lack of prompt studies analysing the atherosclerotic risk in different ethnic groups where the conventional CAD risk predictors undermine the aggravated risk in the Indian Asian population, a survey by Chahal et al. inferred that the burden of subclinical atherosclerosis is inconclusive in predicting risk. Caucasian participants were observed to have a significantly higher intima-media thickness (IMT) than African American participants. Plaque rupture is a prime complication of atherosclerosis, leading to 70% acute MI; there was no discernible difference in plaque between the two ethnic groups.³¹ A cross-sectional study by Anbar et al. further suggests an inconsistency between atherosclerotic CVD risk and atherosclerotic plaque burden, which raises questions about the efficiency of carotid ultrasound in predicting risk in multi-ethnic populations.³²

Vitamin D and Cardiovascular Disease

A study by Smith et al. included 198 male patients without any severe chronic or acute disease of active malignant renal or liver origin between the ages of 40 and 80 years, analysing aortic pulse wave velocity (aPWV) in predicting cardiovascular events in three ethnic groups (African Caribbeans, South Asians and Caucasians) and their relationship with vitamin D and aldosterone levels. South Asians had approximately 0.5 m/s higher adjusted mean aPWV than the other ethnic groups (0.2 m/s), and with the given levels of age and distending pressures, implying a higher risk for CHD in the population. Caucasians had a significantly higher mean level of serum 25-hydroxyvitamin D (21 nmol/l) than South Asians when adjusted for age, weight, season of blood sampling, and vitamin D supplement use. However, there was no significant difference in the aldosterone levels between South Asians and Caucasians after adjusting for antihypertensive use and BMI. The study inferred that serum 25-hydroxyvitamin D was inversely related to aPWV after adjusting for age, systolic blood pressure and diabetes, where age adjustment is a primary factor in participants over 50 years of age.³³

Discussion

This systematic review evaluated the key risk factors contributing to the higher CVD risk among Asian immigrants in the UK. Several studies have identified various risk factors that may contribute to increased CVD risk. These risk factors range from psychological stressors, including depression, anxiety, overcrowding, financial instability, and lack of employment in the Asian group, compared to their Caucasian counterparts. Similarly, genetic risk, including the risk of FH, was higher in the South Asian group. Further, Asians were less active and consumed fewer fruits and vegetables than Caucasians, although the latter group had a higher alcohol intake than Asians. Additionally, Asian participants had a higher disease burden than Caucasians and South Asians, and women also had higher levels of inflammatory markers and endotoxins, which might contribute to higher inflammation and atherosclerosis in this group. Indian Asians and Caucasians had similar risks of subclinical atherosclerosis, and there was no discernible difference in the characteristics between the two groups. Finally, South Asians, mainly women, were more likely to have iron and vitamin B₁₂ deficiency anaemia, whereas Caucasians were more likely to have anaemia of chronic disease. South Asian women with vitamin B₁₂ deficiency have a higher incidence of acute MI.

Kathiresan et al. and Williams et al. provided valuable insights into how psychosocial stressors and acculturation processes contribute to the increased risk of CAD in South Asians in the UK.^17,18

Kathiresan et al. conducted a prospective cohort study using UK Biobank data consisting of 8,420 individuals of South Asian ancestry and 441,696 individuals of European ancestry who were free of baseline cardiometabolic disease. The authors classified South Asians into different acculturation groups based on their length of residence in the UK, noting that those who migrated <5 years were at the highest risk. There was a significant difference in the baseline characteristics between Europeans and South Asians born in the UK and those who lived in the UK for >5 years versus those who were born abroad versus those who lived in the UK for <5 years. These characteristics include differences in systolic and diastolic blood pressure, age, glycated haemoglobin, BMI, number of antihypertensive medications, percentage of smokers, percentage of insulin use, dyslipidaemia, sleep pattern, healthy lifestyle, and sedentary time.¹⁷ South Asians, especially recent immigrants, have a higher risk of cardiometabolic disease after adjusting for traditional risk factors such as age, sex and comorbidities.¹⁷

Williams et al. looked at psychosocial factors in a cross-sectional study enrolling 1,130 South Asian and 818 Caucasian European healthy men and women in west London, aged between 35 and 75 years of age, and concluded that Asians reported significantly higher levels of psychological adversity than their Caucasian counterparts.¹⁸ A cross-sectional study by William et al., consisting of 1,065 healthy South Asian and 818 Caucasian men and women from west London, UK, observed that Muslims experienced higher levels of chronic stress, racial discrimination, socioeconomic deprivation and low social cohesion compared to other South Asian groups. Additionally, Muslim men had lower alcohol consumption and higher smoking rates than Sikhs and Hindus.³⁴ This study also found that Muslims had lowest full-time employment and highest self-employment compared to other ethnic groups and their Caucasian counterparts. Similarly, South Asian families were 10 times more likely to live in overcrowded houses than Caucasian families, with no major difference. Hindus and Sikhs worked slightly longer hours in a week compared to Caucasians and Muslims, and there was less work support available to South Asians compared to their Caucasian counterparts. Muslim and Caucasian participants were more likely to smoke than other South Asian groups.

Stressors such as financial difficulty, family conflict, overcrowding, deprivation and discrimination were common in South Asians. These stressors lead to depression, hostility and low social support, which are established factors for CAD. Stressors can trigger the sympathetic nervous system, inducing inflammatory responses and subsequently affect the endothelium, leading to atherogenesis. Both studies suggest that psychosocial factors contribute significantly to the increased incidence of CHD in South Asians. These stressors may interact with traditional biological risk factors, such as diabetes and HTN, amplifying the risk of CAD. Further research is needed to better understand the complex interplay between psychosocial adversity and biological factors.

Gratton et al. studied the prevalence of FH in different ethnic groups using the UK Biobank, which consisted of 140,439 European, 4,067 South Asian, and 3,906 African participants with lipids. The authors found similarities in the carrier frequency of FH-causing variants in South Asians (1 in 226) and Europeans (1 in 288). South Asians have higher CHD rates despite similar genetic burdens. This suggests that other factors beyond genetics are responsible for increased CHD in this group.¹⁹ They identified 18 and 488 participants of South Asian and European ancestry carrying a likely pathogenic FH variant. Similarly, the self-reported statin use was 55.6% in the FH variant carriers of South Asian ancestry versus 33.8% in Europeans; however, this difference was statistically non-significant.

Similarly, Huang et al. demonstrated that most cardiometabolic loci identified in Europeans were also transferable to South Asians based on the electronic health record data of 22,490 British Bangladeshi and British Pakistani individuals in the Genes and Health community-based cohort study. In particular, polygenic lipids and blood pressure scores showed strong predictive power. However, polygenic scores were less effective in South Asians, which shows the complexity of their genetic makeup.²⁰ Only nine of the 184 well-powered loci were found to be non-transferable, and all nine loci were associated with lipid traits. Cholesteryl ester transfer protein loci were strongly associated with both the HDL and LDL levels in European ancestry samples; however, this association was only found with HDL in the Genes and Health group.

Wang et al. examined whether family history could explain the increased risk of CHD in South Asians; the authors found that individulas with a family history indeed had a higher probability of CHD using the CAC scores, especially among South Asians, despite adjusting for conventional risk factors.²¹ Their findings were based on the analysis of 20-year follow-up data from the Southall and Brent Revisited study.

These three studies suggest that factors beyond family and genetic history contribute to the increased CHD risk in South Asians. This study also found that the association between family history and the number of diagnosed CHD events was weaker in Europeans than in South Asians.²¹ Furthermore, Patel et al. reported a higher prevalence of CVD in South Asian patients, who were predominantly male, had diabetes, chronic kidney disease, a sedentary lifestyle, psychosocial stressors, and lower income compared to their Caucasian counterparts.⁶

Two prospective studies by Eriksen et al. and Williams et al. examined the role of health behaviours as a factor that explains increased coronary heart disease in South Asians in the UK.^22,23 Eriksen et al. followed a cohort of 1,006 South Asians and 1,090 Europeans for 21 years from 1990 to 2011 and noted 346 and 255 CVD events in South Asians and Europeans, respectively. From these events, 313 and 207 were coronary heart disease events in South Asians and Europeans, respectively.²² South Asians tend to be younger at the time of first MI than their Caucasian counterparts, and similar findings were observed in the MASALA study in the US.^35,36

Williams et al. found that physical inactivity in South Asians, especially in Bangladeshis and Pakistanis, contributes significantly to the excess CHD seen in this group. They were less likely to be active than their Caucasian counterparts (47% versus 28.1%), which accounts for over 20% of excess CHD mortality in South Asians. In addition, Pakistanis and Bangladeshis are three times more likely to die from CHD than their Caucasian counterparts (HR 2.87; 95% CI [1.74–4.73]).²³

Eriksen et al. pointed out that poor health behaviours, particularly physical inactivity, contribute to the increased CAD seen in South Asians. This study found that South Asians have a twofold to threefold higher risk of CHD than Europeans. In addition, other behaviours, such as smoking and fruit and vegetable intake, were examined. The authors concluded that these factors could not explain the observed differences between the two groups as they had similar consumption patterns.²² The American Heart Association defined seven modifiable health behaviours and indicators for ideal, intermediate, and poor cardiovascular health, known as “Life’s Simple 7”. These include diet, physical activity, BMI, total cholesterol, fasting glucose, and smoking; surprisingly, none of the participants in the MASALA study achieved ideal levels for all seven metrics. Further, <3% of the participants in this study achieved an optimal diet as recommended by the AHA.³⁷

The two studies cited socioeconomic, cultural and environmental factors as limitations to physical activity among South Asians, mainly Pakistani and Bangladeshi subgroups. These studies highlight the role of physical inactivity in the increased prevalence of CAD in South Asians. A targeted lifestyle programme may help reduce the cardiovascular burden in this group.

Studies by Almuhelm et al., George et al., Tillin et al. and Jones et al. sought to understand whether conventional cardiovascular risk factors such as diabetes, hypertension, high BMI, and lipid profiles, could explain the increased risk in South Asians.^24–27 Several studies have established that South Asians have more cardiovascular risk factors than their Caucasian counterparts.^{24–27,38–40} These risk factors are undeniably more prevalent in South Asians but do not fully explain the differences observed between the two groups. Despite being at high risk for CVD events and dyslipidaemia, South Asians are less likely to be prescribed lipid-lowering therapy for unknown reasons.³⁸ Bangladeshis have the worst outcome from cardiovascular heart disease followed by Pakistanis and Indians and certain risk factors such as a higher prevalence of smoking among Bangladeshi men, lack of physical activity, disadvantaged socioeconomic conditions, and lower consumption of fruits and vegetables and higher consumption of sugary diets may contribute to this.^38,39

Almulhem et al., in a population-based cohort study, found more type 2 diabetes (aHR 3.10; 95% CI [2.97–3.23]) and HTN (aHR 1.34; 95% CI [1.29–1.39]) in Asians than in Europeans.²⁴ Jones et al. also discovered that 15.4% of Caucasians had diabetes compared to 42.1% of South Asians.²⁶ Despite the increased prevalence observed, they offer a limited explanation as to why coronary heart disease is more prevalent in South Asians.²⁴

George et al. and Tillin et al. demonstrated that the increased risk of CHD remains unexplained even after adjusting for these risk factors. Central obesity was more prevalent in South Asians, despite an overall reduced BMI. This is associated with insulin resistance and atherosclerosis, even in the absence of overt obesity.^25,27 Another study based on Norwegian and New Zealand cohorts of patients found that South Asians had an increased age-adjusted risk of CVD compared to their European counterparts, and this risk was 87% versus 92% in the Norwegian cohort and 42% versus 75% in the New Zealand cohort.⁴⁰ South Asians also have a higher risk of diabetes and dyslipidaemia than Europeans, which might explain the increased CVD risk in South Asians.

Almulhem et al. and Tillin et al. noted higher triglyceride levels and central obesity, which could contribute to South Asian susceptibility to CAD.^24,27 However, according to Tillin et al. the conventional risk factors account for only approximately one-third of the increased CHD risk seen in South Asians, suggesting other potential contributing factors, such as genetics, health behaviours, and early life exposures.²⁷ A cohort study by Almulhem et al. also highlighted the importance of considering lifestyle factors and genetics, as they contribute to a higher risk of atherosclerosis.²⁴ Further, Almulhem et al. noted a significantly higher risk of type 2 diabetes, hypertension, IHD and heart failure in Pakistanis and Indians; however, their risk of AF was lower than that of the Caucasians.²⁴ George et al. observed that South Asians were 10 years younger than Caucasian patients, and South Asian patients also had a significantly higher HR for CAD-related events than Caucasian patients.²⁵ Similarly, the risk of ischaemic stroke was also higher for South Asians than for Caucasian patients. Tillin et al. observed that South Asians had a three times greater baseline prevalence of diabetes and were also more centrally obese and dyslipidaemic than Europeans; however, the ethnic differences observed in this study were not sufficient to explain the difference in the incidence of CAD between the two groups.²⁷

Two other studies evaluating the role of immigration on CVD risk among Indian immigrants observed that Indian immigrants in Australia had a more favourable CVD risk profile than Indians in India; however, Patel et al. observed that Indian Gujarati immigrants in the UK were more prone to CVD than Indian Gujaratis, and that this influence could be due to factors such as apolipoprotein B, plasma insulin, and C-reactive protein.^41,42 These four studies collectively concluded that conventional risk factors alone could not explain the increased incidence of CAD in South Asians; a combination of factors such as earlier life exposures, genetic predisposition, and lifestyle likely contribute to the earlier onset and more severe presentation of coronary heart disease seen in this group. Chiu et al. reported that white Canadians are more obese compared to Canadian South Asians; however, the latter group is more likely to have hypertension and diabetes.⁴³ Similarly, the consumption of fruits and vegetables and exercise habits were less commonly observed in the Canadian South Asian group.

Miller et al. conducted a population-based study to examine the role of inflammatory markers, such as endotoxins, and their association with coronary heart disease.²⁸ The findings showed increased endotoxin levels in South Asians compared to Caucasians, with the lowest level observed in black participants (p<0.01). It was positively correlated with metabolic syndrome markers, including waist circumference, waist–hip ratio, total cholesterol, triglycerides, and insulin levels. Similarly, the level of endotoxins is lower in women than in men. Interestingly, high-sensitivity C-reactive protein correlates with endotoxins, which explains why endotoxaemia may exacerbate inflammatory processes in South African individuals. In addition, a population-based study showed a stronger relationship between endotoxins and cardiovascular risk factors in South Asians than in Caucasians.

Chackathayil et al. evaluated the role of anaemia in CVDs.²⁹ The study examined the prevalence of IDA and vitamin B₁₂ deficiency and found that they are both higher among South Asians living in the UK than among their Caucasian counterparts. Notably, South Asian women showed a significant increase in anaemia, which affected their cardiovascular profiles. The study, which was a retrospective cross-sectional analysis of University of Birmingham hospital cases, found that there is a complex relationship between anaemia and CHD in South Asians. For instance, IDA, which is associated with a higher prevalence of diabetes, is paradoxically linked to a reduced prevalence of MI and IHD in South Asian women. Therefore, it appears to protect this group against IHD in premenopausal women. Conversely, South Asian women with B₁₂ deficiency had a higher prevalence of MI and IHD than those without.

The increased prevalence of IDA and vitamin B₁₂ deficiency, mainly caused by nutrition, could worsen the already increased diabetes and heart disease. While IDA appears to confer paradoxical protection against CVD, vitamin B₁₂ deficiency increases the burden. Therefore, this study calls for a more focused healthcare strategy for managing anaemia in these groups.²⁹ Further research is needed to explore the mechanisms underlying this relationship which can then help in the development of targeted preventive and therapeutic measures.

The increased risk of CHD in South Asians living in the UK cannot be fully explained by measures of atherosclerosis, such as coronary artery calcification, carotid intima-media thickness (cIMT), or plaque burden. Jain et al., Chahal et al., and more recently, Anbar et al. observed that factors beyond atherosclerotic plaque burden may drive the increased risk.^30–32

Jain et al. found no significant differences in CAC scores or silent MI between the two ethnic groups (Indian Asians versus Caucasians).³⁰ Similarly, Chahal et al. found no significant differences in subclinical atherosclerosis, as measured by the presence of plaque and IMT, between these two ethnic groups, despite the higher rates of diabetes and HTN in Indian Asians.³¹

Anbar et al. provided further evidence to explain this paradox by comparing the prevalence of carotid atherosclerosis among South Asian, European Asian, and African Caribbean populations. The study found similar plaque prevalence between South Asians and Europeans (16%) after measuring cardiovascular risk factors and performing carotid ultrasonography.³² This shows that while cIMT and carotid plaque burden are valuable for assessing atherosclerosis, they are unreliable predictors of CHD risk in South Asians. Therefore, these studies collectively highlight the failure of atherosclerosis to fully explain the increased CHD risk in South Asian individuals in the UK.

Rezai et al. explored the role of vitamin D in explaining ethnic differences in aPWV, a marker of arterial stiffness and a predictor of cardiovascular events.³³ Vitamin D deficiency partly explains the increased risk of CHD in South Asians. After adjusting for age, systolic blood pressure and diabetes, South Asians had a higher aPWV (mean 0.5 m/s) and lower vitamin D levels than Europeans by an average of 21 nmol/l.

Interestingly, the study also found that regional differences in aPWV were more pronounced in the descending aorta, where values in South Asians were 0.8 m/s higher than those in Europeans.³³ This, in turn, reflects the differential vascular remodelling potentially influenced by vitamin D, which plays a role in modulating vascular calcification, endothelial function, and the renin–angiotensin–aldosterone system. This provides further evidence for the role of vitamin D deficiency in explaining ethnic differences in aortic stiffness and CHD risk.

Study Strengths

This study has several strengths. First, it is one of the few studies focusing on the various risk factors attributed to the higher CVD risk among South Asians living in the UK. Second, it is a systematic review based on the most recent data and studies published until 2025. Further, it provides an opportunity to address these risk factors and can also help guide future research, focusing on the higher-risk factors contributing to a higher CVD risk in this population group. Finally, this systematic review, despite including cross-sectional studies, highlights various risk factors for intervention that may reduce CVD risk in South Asians through early intervention.

Study Limitations

While this systematic review has shed important light on why South Asians living in the UK have increased CAD than their Caucasian counterparts, there are some limitations to these studies that need to be considered, most prominently methodological constraints. Many of the studies employed are cross-sectional, making it difficult to establish causality. For instance, studies evaluating the role of psychological factors, health behaviours, and inflammatory markers are all cross-sectional, limiting the ability to determine the direction of the relationships. Moreover, the studies were UK-based, which limits the generalisability of their findings, as they may not apply to South Asians in countries with different healthcare systems or lifestyle practices.

Cultural biases and reliance on self-reports are additional concerns. Cultural factors may have influenced the results of some studies. For example, South Asians may underreport psychosocial stress due to cultural expectations regarding emotional expression or perceived social stigma. In addition, reliance on self-reporting for lifestyle choices, such as smoking, diet and physical activity, may be impacted by recall bias. In addition, the sample size and representation within the South Asian population are limitations. A good example is the study of genetic predisposition, which often underrepresents non-European ancestries; this is critical for appreciating population-specific genetic contributions to CAD.

Future Research Directions and Recommendations

Future research can address these constraints through larger longitudinal studies that demonstrate causality and directly measure relationships. Additionally, studies should include a broader South Asian subgroup, given the heterogeneity observed in this group. For instance, understanding the differences in CAD risk between Indian, Pakistani, Bangladeshi, and Sri Lankan populations could provide more specific insights. This systematic review showed the multifaceted nature of CAD risk. Therefore, future studies should adopt a more integrated approach that links genetics and psychosocial, lifestyle, and environmental factors, which could provide a better understanding of the drivers of CAD risk in South Asian populations. Future studies should investigate the potential mechanisms by which vitamin D affects cardiovascular health, including its impact on endothelial function and arterial stiffness. In addition, randomised controlled trials could establish whether vitamin D supplementation can reduce the risk of CAD in high-risk groups. Therefore, exploring the relationship between atherosclerosis, systemic inflammation and CAD is warranted. Although traditional imaging techniques, such as cIMT, provide some information, they may not fully explain ethnic disparities in CAD.

Conclusion

The increased risk of CAD among South Asians in the UK is multifactorial, with genetic, environmental, psychosocial, and behavioural factors all being linked. While conventional risk factors such as diabetes and hypertension are more prevalent in South Asians, they do not fully explain the elevated CAD risk. Moreover, psychosocial stressors, lifestyle behaviours, inflammatory markers, and deficiencies in key nutrients, such as vitamins D and B₁₂, further contribute to this disparity. Given the complexity of these factors, further research is needed to better understand these intricate interactions and develop targeted interventions that address both the biological and sociocultural challenges faced by the South Asian population.

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