Risk of metabolic and vascular disease in South Asians: potential mechanisms for increased insulin resistance

Retrospective cohort study of the association between socioeconomic deprivation and incidence of gestational diabetes and perinatal outcomes

INTRODUCTION

Socioeconomic disparities have been shown to correlate with perinatal mortality and the incidence of type 2 diabetes. Few studies have explored the relationship between deprivation and the incidence of gestational diabetes (GDM). We aimed to identify the relationship between deprivation and incidence of GDM, after adjusting for age, BMI, and ethnicity. We also examined for relationships between deprivation and perinatal outcomes.

METHODS

A retrospective cohort analysis of 23,490 pregnancies from a major National Health Service Trust in Northwest London was conducted. The 2019 English Indices of Multiple Deprivation was used to identify the deprivation rank and decile for each postcode. Birthweight centile was calculated from absolute birthweight after adjusting for ethnicity, maternal height, maternal weight, parity, sex and outcome (live birth/stillbirth). Logistic regression and Kendall's Tau were used to identify relationships between variables.

RESULTS

After controlling for age, BMI & ethnicity, Index of Multiple Deprivation postcode decile was not associated with an increased risk of developing gestational diabetes. Each increase in decile of deprivation was associated with an increase in birthweight centile by 0.471 (p < 0.001). After adjusting for confounders, age was associated with a 7.1% increased GDM risk (OR: 1.076, p < 0.001); BMI increased risk by 5.81% (OR: 1.059, p < 0.001). There was no significant correlation between Index of Multiple Deprivation rank and perinatal outcomes.

DISCUSSION

Our analysis demonstrates that socioeconomic deprivation was not associated with incidence of GDM or adverse perinatal outcomes. Factors such as genetic predisposition and lifestyle habits may likely play a larger role in the development of GDM compared to socioeconomic deprivation alone.

Role of diabetes in stroke: Recent advances in pathophysiology and clinical management

The increasing prevalence of diabetes and stroke is a major global public health concern. Specifically, acute stroke patients, with pre-existing diabetes, pose a clinical challenge. It is established that diabetes is associated with a worse prognosis after acute stroke and the various biological factors that mediate poor recovery profiles in diabetic patients is unknown. The level of association and impact of diabetes, in the setting of reperfusion therapy, is yet to be determined. This article presents a comprehensive overview of the current knowledge of the role of diabetes in stroke, therapeutic strategies for primary and secondary prevention of cardiovascular disease and/or stroke in diabetes, and various therapeutic considerations that may apply during pre-stroke, acute, sub-acute and post-stroke stages. The early diagnosis of diabetes as a comorbidity for stroke, as well as tailored post-stroke management of diabetes, is pivotal to our efforts to limit the burden. Increasing awareness and involvement of neurologists in the management of diabetes and other cardiovascular risk factors is desirable towards improving stroke prevention and efficacy of reperfusion therapy in acute stroke patients with diabetes.

Beyond Asian-Specific Cutoffs: Gender Effects on the Predictability of Body Mass Index, Waist Circumference, and Waist Circumference to Height Ratio on Hemoglobin A1c

OBJECTIVES

This study examines the gender effect on the associations between body mass index (BMI), waist circumference (WC), and waist circumference to height ratio (WHtR) with hemoglobin A1c (HbA1c) when Asian-specific cutoffs are applied among Asians living in the USA.

DESIGN

This study used the pooled 2013-2014 and 2015-2016 National Health and Nutrition Examination Survey (NHANES) data to produce a sample of 900 Asians who were non-pregnant and non-Hispanic aged 20-65. Bivariate and general linear regression analyses were conducted based on gender and age group.

RESULTS

The group variations of BMI, WC, and WHtR all exhibited different patterns between males and females. Among the bivariate correlations with HbA1c, WHtR was the strongest in males and WC was the strongest in females. All three measures performed better in predicting HbA1c among younger Asians. WC predicted more of the variance in HbA1c among females, whereas WHtR predicted more of the variance in HbA1c among males.

CONCLUSIONS

WC and WHtR are two anthropometric measures that serve as appropriate proxy of HbA1c for gauging the risk of developing type 2 diabetes among Asians living in the USA. They can be easily performed at non-clinical settings and should be used by individuals to monitor their health and be a part of disease prevention.

Is waist circumference more strongly associated with metabolic risk factors than waist-to-height ratio in Asians?

OBJECTIVES

Differential distribution of fats can vary among ethnic groups and thus have varying effects on metabolic risk. Measuring metabolic risk of individuals using simple anthropometric measurements is essential to replace current invasive methods of obtaining blood samples. Waist-to-height ratio (WHtR) has been advocated as the best simple anthropometric measurement, but, because of the high visceral fat of Asians, there has been speculation as to the possibility of using only waist circumference (WC) to measure metabolic risk. The aim of this study was to compare the performance of WC and WHtR in terms of their association with measures of obesity and metabolic risk factors (e.g., homeostasis model assessment for insulin resistance, low-density lipoprotein, triacylglycerol, and ratio of triacylglycerol to high-density lipoprotein) and to obtain an optimal cutoff value for one anthropometric measurement.

METHODS

The study was performed on healthy Asian Chinese (N = 527) men (n = 209) and women (n = 318) who participated in a cross-sectional study conducted at the Clinical Nutrition Research Centre located in Singapore. Association of WC and WHtR with metabolic risk factors was obtained using Spearman's rank correlation coefficient. Optimal cutoff value was obtained using receiver operating characteristic curve.

RESULTS

WC and WHtR performed equally well in both sexes in terms of their strength of association between metabolic risk factors. Receiver operating characteristic curve analysis showed that 73.5 cm (in women) and 82.5 cm (in men) were the optimal WC cutoff values to identify insulin resistance.

CONCLUSION

It is suggested that WC is a simpler anthropometric measurement that has strong association with an individual's metabolic risk level.

South Asians: why are they at a higher risk for cardiovascular disease?

PURPOSE OF REVIEW

We comment on the high prevalence of cardiovascular disease (CVD) in South Asians (SA). The effect of various risk factors, for example biochemical, genetic, lifestyle, socioeconomic factors and psychosocial stress on CVD risk is discussed.

RECENT FINDINGS

'Prediabetes' is common in SA, but its relationship with coronary artery disease (CAD) is not significant unlike for the white population. At the same time, 'prediabetes' in SA is associated with an increased risk for cerebrovascular disease (CeVD). The differentiating factor could be the high lipids in Europeans and their relationship to CAD. Likewise, higher diastolic blood pressure in SA may explain the risk of CeVD. Small, dense, low-density lipoprotein (LDL), low high-density lipoprotein-cholesterol (HDL-C) concentration and high triglycerides may contribute to atherosclerosis. Thrombotic factors such as increased levels of plasminogen activator inhibitor, fibrinogen, lipoprotein (a) and homocysteine have been shown to be associated with increased CVD. Impaired cerebrovascular autoregulation and sympathovagal activity, increased arterial stiffness and endothelial dysfunction may increase CVD risk further. In addition, environmental and dietary factors may exaggerate the unfavourable cardiovascular profile through genetic factors.

SUMMARY

The implications of the findings suggest comprehensive screening of SA for CVD. Cultural differences should be considered while designing prevention strategies specifically targeting barriers for uptake of preventive service.

"I'm Managing My Diabetes between Two Worlds": Beliefs and Experiences of Diabetes Management in British South Asians on Holiday in the East--A Qualitative Study

BACKGROUND

Diabetes is disproportionately high among British South Asians compared to the general UK population. Whilst the migrant British South Asians group has received most attention on research related to diabetes management, little consideration has been given to impact of travel back to the East. This study aimed to explore the role of social networks and beliefs about diabetes in British South Asians, to better understand their management behaviours whilst holidaying in the East.

METHODS

Semistructured interviews were conducted in Greater Manchester. Forty-four participants were recruited using random and purposive sampling techniques. Interviews were analysed thematically using a constant comparison approach.

RESULTS

Migrant British South Asians expressed a strong preference to be in a hot climate; they felt they had a healthier lifestyle in the East and often altered or abandoned their diabetes medication. Information acquisition on diabetes and availability of social networks in the East was valued.

CONCLUSION

Social networks in the East are a valued source of information and support for diabetes. The lack of adherence to medication whilst abroad suggests that some migrant British South Asians have a poor understanding of diabetes. Future research needs to explore whether patients are seeking professional advice on diabetes management prior to their extended holiday.

An investigation of two-dimensional ultrasound carotid plaque presence and intima media thickness in middle-aged South Asian and European men living in the United kingdom

Objectives

Ultrasound studies of carotid intima media thickness (cIMT) and plaques are limited in South Asians, a group at elevated cardiovascular disease (CVD) risk. We determined whether South Asians have a difference in these ultrasound markers compared to Europeans living in the United Kingdom and whether measured risk factor(s) could account for any such differences.

Methods

One hundred South Asian men, aged 40 to 70 years and 100 European men of similar age and BMI, without diagnosed CVD or diabetes, underwent carotid ultrasound for measurement of cIMT and carotid plaque presence. Physical activity, cardiorespiratory fitness, anthropometry and blood pressure were assessed, fasted blood taken for measurement of cardiometabolic risk factors and demographic and lifestyle factors recorded.

Results

Age-adjusted mean (SD) cIMT was similar in South Asians and Europeans (0.64 (0.16) mm v 0.65 (0.12) mm, p = 0.64). Plaque was present in 48 South Asians and 37 Europeans and overall, there was no age-adjusted difference between South Asian and Europeans for plaque score(odds ratio 1.49, 95% CI, 0.86-2.80, p = 0.16), however, South Asians appeared to have more plaques at a younger age than Europeans; at age 40-50 years the odds of South Asians having plaques was 2.63 (95% CI, 1.16-5.93) times that for Europeans.

Conclusions

cIMT is similar between healthy South Asian and European men. Whilst there was no overall difference in plaque presence in South Asians, there is an indication of greater plaque prevalence at younger ages - an observation requiring further investigation. Prospective studies linking plaques to CVD outcomes in South Asians are needed to investigate whether these measures help improve CVD risk prediction.

Ethnic differences in glycaemic control in people with type 2 diabetes mellitus living in Scotland

Background and Aims

Previous studies have investigated the association between ethnicity and processes of care and intermediate outcomes of diabetes, but there are limited population-based studies available. The aim of this study was to use population-based data to investigate the relationships between ethnicity and glycaemic control in men and women with diabetes mellitus living in Scotland

Methods

We used a 2008 extract from the population-based national electronic diabetes database of Scotland. The association between ethnicity with mean glycaemic control in type 2 diabetes mellitus was examined in a retrospective cohort study, including adjustment for a number of variables including age, sex, socioeconomic status, body mass index (BMI), prescribed treatment and duration of diabetes.

Results

Complete data for analyses were available for 56,333 White Scottish adults, 2,535 Pakistanis, 857 Indians, 427 Chinese and 223 African-Caribbeans. All other ethnic groups had significantly (p<0.05) greater proportions of people with suboptimal glycaemic control (HbA1c >58 mmol/mol, 7.5%) compared to the White Scottish group, despite generally younger mean age and lower BMI. Fully adjusted odds ratios for suboptimal glycaemic control were significantly higher among Pakistanis and Indians (1.85, 95% CI: 1.68–2.04, and 1.62,95% CI: 1.38–1.89) respectively.

Conclusions

Pakistanis and Indians with type 2 diabetes mellitus were more likely to have suboptimal glycaemic control than the white Scottish population. Further research on health services and self-management are needed to understand the association between ethnicity and glycaemic control to address ethnic disparities in glycaemic control.

Should physical activity recommendations be ethnicity-specific? Evidence from a cross-sectional study of South Asian and European men

BACKGROUND

Expert bodies and health organisations recommend that adults undertake at least 150 min.week(-1) of moderate-intensity physical activity (MPA). However, the underpinning data largely emanate from studies of populations of European descent. It is unclear whether this level of activity is appropriate for other ethnic groups, particularly South Asians, who have increased cardio-metabolic disease risk compared to Europeans. The aim of this study was to explore the level of MPA required in South Asians to confer a similar cardio-metabolic risk profile to that observed in Europeans undertaking the currently recommended MPA level of 150 min.week(-1).

METHODS

Seventy-five South Asian and 83 European men, aged 40-70, without cardiovascular disease or diabetes had fasted blood taken, blood pressure measured, physical activity assessed objectively (using accelerometry), and anthropometric measures made. Factor analysis was used to summarise measured risk biomarkers into underlying latent 'factors' for glycaemia, insulin resistance, lipid metabolism, blood pressure, and overall cardio-metabolic risk. Age-adjusted regression models were used to determine the equivalent level of MPA (in bouts of ≥ 10 minutes) in South Asians needed to elicit the same value in each factor as Europeans undertaking 150 min.week(-1) MPA.

FINDINGS

For all factors, except blood pressure, equivalent MPA values in South Asians were significantly higher than 150 min.week(-1); the equivalent MPA value for the overall cardio-metabolic risk factor was 266 (95% CI 185-347) min.week(-1).

CONCLUSIONS

South Asian men may need to undertake greater levels of MPA than Europeans to exhibit a similar cardio-metabolic risk profile, suggesting that a conceptual case can be made for ethnicity-specific physical activity guidance. Further study is needed to extend these findings to women and to replicate them prospectively in a larger cohort.

A four-stage model explaining the higher risk of Type 2 diabetes mellitus in South Asians compared with European populations

With approximately 1.5 billion people at risk, the staggeringly high risk of Type 2 diabetes in South Asians comprises a global problem. The causes of this high risk are complex, with 23 major risk factors identified in a Lancet seminar. This paper proposes a four-stage explanatory model: (1) the birth of a small, adipose, lowlean mass South Asian baby--the phenotype tracking through life; (2) in childhood and early adulthood, the deposition of any excess energy intake preferentially in upper body and ectopic fat stores rather than in the lower body or superficial subcutaneous fat stores; (3) as a consequence of points 1 and 2, and exacerbated by an environment of low physical activity and excess calories, the accelerated appearance of high levels of plasma insulin, triglycerides and glucose, and the fatty-liver vicious cycle; (4) β-cell failure as a result of fewer β-cells at birth, exposure to apoptotic triggers such as fat in the pancreas, and high demand from insulin resistance, which causes diabetes. Other risk factors--especially energy-dense hyperglycaemic diet and low physical activity--play into this pathway. The recommended behavioural changes fit with this model, which brings clarity to guide future research, policy, practice and health promotion.

Existing maternal obesity guidelines may increase inequalities between ethnic groups: a national epidemiological study of 502,474 births in England

BACKGROUND

Asians are at increased risk of morbidity at a lower body mass index (BMI) than European Whites, particularly relating to metabolic risk. UK maternal obesity guidelines use general population BMI criteria to define obesity, which do not represent the risk of morbidity among Asian populations. This study compares incidence of first trimester obesity using Asian-specific and general population BMI criteria.

METHOD

A retrospective epidemiological study of 502,474 births between 1995 and 2007, from 34 maternity units across England. Data analyses included a comparison of trends over time between ethnic groups using Asian-specific and general population BMI criteria. Logistic regression estimated odds ratios for first trimester obesity among ethnic groups following adjustment for population demographics.

RESULTS

Black and South Asian women have a higher incidence of first trimester obesity compared with White women. This is most pronounced for Pakistani women following adjustment for population structure (OR 2.19, 95% C.I. 2.08, 2.31). There is a twofold increase in the proportion of South Asian women classified as obese when using the Asian-specific BMI criteria rather than general population BMI criteria. The incidence of obesity among Black women is increasing at the most rapid rate over time (p=0.01).

CONCLUSION

The twofold increase in maternal obesity among South Asians when using Asian-specific BMI criteria highlights inequalities among pregnant women. A large proportion of South Asian women are potentially being wrongly assigned to low risk care using current UK guidelines to classify obesity and determine care requirements. Further research is required to identify if there is any improvement in pregnancy outcomes if Asian-specific BMI criteria are utilised in the clinical management of maternal obesity to ensure the best quality of care is provided for women irrespective of ethnicity.

The association of the triglyceride-to-HDL cholesterol ratio with insulin resistance in White European and South Asian men and women

INTRODUCTION

There is recent interest surrounding the use of the triglyceride-to-HDL cholesterol ratio as a surrogate marker of insulin resistance in clinical practice, as it may identify people at high risk of developing diabetes or its complications. However, it has been suggested using this lipid ratio may not be appropriate for measuring insulin resistance in African-Americans, particularly women. We investigated if this inconsistency extended to South Asian women in a UK multi-ethnic cohort of White Europeans and South Asians.

METHODS

Cross-sectional analysis was done of 729 participants from the ADDITION-Leicester study from 2005 to 2009. The association between tertiles of triglyceride-to-HDL cholesterol ratio to fasting insulin, homeostatic model of assessment for insulin resistance (HOMA1-IR), quantitative insulin sensitivity check index (QUICKI) and glucose: insulin ratio was examined with adjustment for confounding variables.

RESULTS

Incremental tertiles of the triglyceride-to-HDL cholesterol ratio demonstrated a significant positive association with levels of fasting insulin, HOMA1-IR, glucose: insulin ratio and a negative association with QUICKI in White European men (n = 255) and women (n = 250) and South Asian men (n = 124) (all p<0.05), but not South Asian women (n = 100). A significant interaction was demonstrated between sex and triglyceride-to-HDL cholesterol ratio tertiles in South Asians only (p<0.05). The area under the receiver operating characteristic curve for triglyceride-to-HDL cholesterol ratio to detect insulin resistance, defined as the cohort HOMA1-IR ≥ 75(th) percentile (3.08), was 0.74 (0.67 to 0.81), 0.72 (0.65 to 0.79), 0.75 (0.66 to 0.85) and 0.67 (0.56 to 0.78) in White European men and women, South Asian men and women respectively. The optimal cut-points for detecting insulin resistance were 0.9-1.7 in mmol/l (2.0-3.8 in mg/dl) for the triglyceride-to-HDL ratio.

CONCLUSION

In South Asian women the triglyceride-to-HDL cholesterol ratio was not associated with insulin resistance; therefore there may be limitations in its use as a surrogate marker in this group.

Sitting time and waist circumference are associated with glycemia in U.K. South Asians: data from 1,228 adults screened for the PODOSA trial

OBJECTIVE

To investigate the independent contributions of waist circumference, physical activity, and sedentary behavior on glycemia in South Asians living in Scotland.

RESEARCH DESIGN AND METHODS

Participants were 1,228 (523 men and 705 women) adults of Indian or Pakistani origin screened for the Prevention of Type 2 Diabetes and Obesity in South Asians (PODOSA) trial. All undertook an oral glucose tolerance test, had physical activity and sitting time assessed by International Physical Activity Questionnaire, and had waist circumference measured.

RESULTS

Mean ± SD age and waist circumference were 49.8 ± 10.1 years and 99.2 ± 10.2 cm, respectively. One hundred ninety-one participants had impaired fasting glycemia or impaired glucose tolerance, and 97 had possible type 2 diabetes. In multivariate regression analysis, age (0.012 mmol ⋅ L⁻¹ ⋅ year⁻¹ [95% CI 0.006-0.017]) and waist circumference (0.018 mmol ⋅ L⁻¹ ⋅ cm⁻¹ [0.012-0.024]) were significantly independently associated with fasting glucose concentration, and age (0.032 mmol ⋅ L⁻¹ ⋅ year⁻¹ [0.016-0.049]), waist (0.057 mmol ⋅ L⁻¹ ⋅ cm⁻¹ [0.040-0.074]), and sitting time (0.097 mmol ⋅ L⁻¹ ⋅ h⁻¹ ⋅ day⁻¹ [0.036-0.158]) were significantly independently associated with 2-h glucose concentration. Vigorous activity time had a borderline significant association with 2-h glucose concentration (-0.819 mmol ⋅ L⁻¹ ⋅ h⁻¹ ⋅ day⁻¹ [-1.672 to 0.034]) in the multivariate model.

CONCLUSIONS

These data highlight an important relationship between sitting time and 2-h glucose levels in U.K. South Asians, independent of physical activity and waist circumference. Although the data are cross-sectional and thus do not permit firm conclusions about causality to be drawn, the results suggest that further study investigating the effects of sitting time on glycemia and other aspects of metabolic risk in South Asian populations is warranted.

Type 2 diabetes and cardiovascular disease in South Asians

Type 2 diabetes (T2DM) is growing at a pandemic scale and is associated with a rapid increase in its complications such as cardiovascular diseases (CVD). This problem is even worse in South Asian population with South Asian people having a much higher prevalence of T2DM and CVD, occurring at an earlier age and being associated with premature and high mortality. This review looks in detail at the current knowledge on epidemiology and characteristic pathophysiology of T2DM and CVD (coronary heart disease, heart failure, stroke and peripheral vascular disease) in South Asian migrant population. Specific attention is also drawn to the role of novel risk factors and cultural and socioeconomic factors on occurrence and outcomes of these chronic diseases in this population. Finally the review makes recommendations on various measures including need for further research to tackle this serious health challenge facing the South Asian community.

Early emergence of ethnic differences in type 2 diabetes precursors in the UK: the Child Heart and Health Study in England (CHASE Study)

BACKGROUND

Adults of South Asian origin living in the United Kingdom have high risks of type 2 diabetes and central obesity; raised circulating insulin, triglyceride, and C-reactive protein concentrations; and low HDL-cholesterol when compared with white Europeans. Adults of African-Caribbean origin living in the UK have smaller increases in type 2 diabetes risk, raised circulating insulin and HDL-cholesterol, and low triglyceride and C-reactive protein concentrations. We examined whether corresponding ethnic differences were apparent in childhood.

METHODS AND FINDINGS

We performed a cross-sectional survey of 4,796 children aged 9-10 y in three UK cities who had anthropometric measurements (68% response) and provided blood samples (58% response); ethnicity was based on parental definition. In age-adjusted comparisons with white Europeans (n = 1,153), South Asian children (n = 1,306) had higher glycated haemoglobin (HbA1c) (% difference: 2.1, 95% CI 1.6 to 2.7), fasting insulin (% difference 30.0, 95% CI 23.4 to 36.9), triglyceride (% difference 12.9, 95% CI 9.4 to 16.5), and C-reactive protein (% difference 43.3, 95% CI 28.6 to 59.7), and lower HDL-cholesterol (% difference -2.9, 95% CI -4.5 to -1.3). Higher adiposity levels among South Asians (based on skinfolds and bioimpedance) did not account for these patterns. Black African-Caribbean children (n = 1,215) had higher levels of HbA1c, insulin, and C-reactive protein than white Europeans, though the ethnic differences were not as marked as in South Asians. Black African-Caribbean children had higher HDL-cholesterol and lower triglyceride levels than white Europeans; adiposity markers were not increased.

CONCLUSIONS

Ethnic differences in type 2 diabetes precursors, mostly following adult patterns, are apparent in UK children in the first decade. Some key determinants operate before adult life and may provide scope for early prevention.