FAMILY INCOME AND ADOLESCENT BLOOD PRESSURE IN A CHINESE BIRTH COHORT: “CHILDREN OF 1997”

Lack of inconsistency in the relation of national income and population mean blood pressure (BP) highlights the importance of contextually specific understanding on whether and how individual income affects blood pressure. Income confers not only the ability to purchase material resources but also the capability to possess symbolic resources. Social comparisons of income (relative income) or position (relative rank) may be more relevant than income per se (absolute income), particularly in settings with higher income disparities. In a developed non-Western setting with a high Gini co-efficient, we prospectively examined the associations of family income (accounting for family size) at birth with BP z-score at ~13 years relative to sex-, age- and height-specific references for contemporary US children in a population-representative Chinese birth cohort, Hong Kong’s “Children of 1997” (n=4,925). Higher Yitzhaki index of relative deprivation in income in units of HKD 1,000 (USD 129) (income difference between own and others with higher income), i.e., more deprivation was associated with higher diastolic BP (0.02 mmHg, 95% CI 0.001, 0.03), but not systolic BP. Higher relative rank in income (percentile position in the income distribution) was associated with lower systolic BP (-0.01 mmHg, 95% CI -0.20, -0.002) and with lower diastolic BP (-0.09 mmHg, 95% CI -0.14, 0.04). Absolute income (continuous) was not associated with BP. In a developed non-Western setting, relative income and relative rank, rather than absolute income, were associated with higher adolescent BP, suggesting limited access to socially desirable resources or psychological stress arising from social comparisons could have implications for cardiovascular health.