Life course socioeconomic influences on risk of cardiovascular disease in low- and middle-income countries

Background: Cardiovascular disease is the leading cause of premature death in most low- and middle-income countries. Studies suggest that socioeconomic factors acting at various points in an individual’s life course can strongly influence their later risk of cardiovascular disease. However, evidence is mostly from high-income countries, and may not generalise to low- and middle-income countries where the material conditions associated with low socioeconomic position, and the socioeconomic patterning of risk factors, are distinct. Given the limited data on cardiovascular disease from low- and middle-income countries, there remain substantial gaps in our knowledge around the association between socioeconomic factors across the life course and risk of cardiovascular disease. This thesis aims to identify and fill several evidence gaps in this area by reviewing the existing evidence and analysing secondary data from two populous middle-income countries. Objectives (corresponding to specific evidence gaps identified for low- and middle-income countries): (1) To examine the association between socioeconomic position in adulthood and cardiovascular mortality (method: analysis of the states of Brazil using national mortality and census data) (2) To summarise the existing evidence on socioeconomic position in childhood and risk of cardiovascular disease in adulthood (method: systematic literature review) (3) To evaluate the association between socioeconomic position in childhood and risk of cardiovascular disease in adulthood (method: analysis of pooled cohorts from India) (4) To evaluate the association between parents’ socioeconomic position in childhood and risk of cardiovascular disease in their adult offspring (method: analysis of an intergenerational cohort in rural India) Findings: Evidence from the states of Brazil suggests that lower socioeconomic groups are at a higher risk of cardiovascular mortality regardless of the stage of area-level economic development. Through a systematic review, I identified limited evidence on the association between childhood socioeconomic position and cardiovascular disease, while studies of cardiovascular risk factors showed little consistent evidence for an association. In India, I found some evidence to support an association between childhood poverty and increased blood pressure (but not other cardiovascular risk factors); however, there was no evidence of an intergenerational effect of parents’ poverty in childhood on cardiovascular risk factors or subclinical atherosclerosis in their adult offspring. Conclusion: Limited evidence indicates that lower socioeconomic groups face a higher risk of mortality from cardiovascular disease across low- and middle-income countries. Childhood and intergenerational poverty appear to play a limited role in explaining this excess risk. Further evidence, especially from low- and lower middle-income countries, and with prospective measures of life course socioeconomic position and cardiovascular disease incidence and mortality, are needed to confirm these findings and elucidate possible mechanisms. In the meantime, policies to prevent cardiovascular disease in low- and middle-income countries should be oriented towards reducing the risk in lower socioeconomic groups, for example by reducing tobacco use, improving air quality, and promoting equitable access to cardiovascular disease treatments.