Diet and risk of acute myocardial infarction in Bangladesh: The Bangladesh Risk of Acute Vascular Events (BRAVE) study

SUMMARY Name: Sara Shahzad Title: Diet and risk of acute myocardial infarction in Bangladesh: the Bangladesh Risk of Acute Vascular Events (BRAVE) study Background Coronary Heart Disease (CHD), with myocardial infarction (MI) as its main manifestation, is increasing at an alarming rate in South Asian countries, however evidence on its determinants is sparse. Dietary risk explains about one-third of global mortality and is a most important modifiable risk factor for CHD. Although there is extensive evidence on diet and risk of CHD from western populations, this cannot be generalised to South Asian populations where the dietary habits are very diverse. Objectives: The main aims of this thesis are to (1) summarise existing epidemiological evidence on diet and risk of CHD in South Asians; (2) characterise in detail the lifestyle socio-demographic and other correlates of dietary factors in a South Asian population; (3) investigate the association of dietary food groups, patterns and nutrients with the risk of MI and (4) discuss public health implications of the findings. Methods: BRAVE is a hospital-based case-control study from Dhaka, Bangladesh which has about 8000 cases and 8000 controls frequency matched by age and sex. This study has overlapping data looking at lifestyle (including dietary determinants), biochemical, genetic and environmental risk factors for acute MI (AMI). Using data from this study dietary determinants of AMI were investigated through (1) cross-sectional analyses of the association of diet with various correlates and (2) case-control analyses with risk of MI. Results: The systematic review demonstrated that there was scarce evidence on diet and risk of CHD from South Asia. Cross-sectional analyses from BRAVE study demonstrated that dietary food groups, patterns and nutrients had different associations with the various characteristics showing the role of modest confounding. There were few strong correlations between food groups, nutrients and dietary patterns. Findings from food group analyses showed an inverse association between fruits, vegetables, yoghurt, certain spices and risk of AMI. In contrast, higher consumption of biryani and fish was associated with higher risk of AMI. Three distinct dietary patterns were identified using principal component analysis; the “energy dense pattern”, the “vegetable pattern” and the “fruits and dairy pattern”. The vegetable pattern and fruit and dairy pattern had an inverse association with the risk of AMI. In contrast, “energy dense pattern” had no significant association with the risk of AMI. As for the analyses on dietary nutrients, higher intake of refined carbohydrates was not associated with the risk of AMI, while non-refined carbohydrates were associated with lower risk of AMI. Animal protein showed a higher risk of AMI, whereas plant protein showed a weak inverse association. As for specific fatty acids, modest intakes of saturated fatty acid from dairy sources and polyunsaturated fatty acids were associated with a slightly lower risk of AMI. In contrast monounsaturated fatty acids showed an increased association only in highest quintile. Conclusions: The present analyses are the largest detailed study on diet and CHD solely based on a South Asian population. It confirms previous observed association of some food groups with CHD in western populations and has also yielded some novel insights on the association of diet with CHD specific to Bangladesh. However, owing to an observational nature of the study a causal assessment could not be done, findings of this study stimulates further detailed work including prospective cohort studies which may have important potentials for the local dietary guidelines in Bangladesh and in similar settings to help reduce the rising burden of CHD