Lifecourse socioeconomic trajectories and C-reactive protein levels in young adults: findings from a Brazilian birth cohort

Abstract

Socioeconomic factors are associated with cardiovascular disease. C-reactive protein (CRP) is increasingly implicated as a candidate linking conventional risk factors and atherosclerosis. The impact of early- and later-life socioeconomic status (SES) on CRP levels has not been widely investigated and a handful of studies from high-income countries are inconsistent. We set out to examine the associations between lifecourse socioeconomic indicators (family income at birth, maternal education, family income at age 23 and own education) on CRP levels in young adults belonging to the 1982 Pelotas (Brazil) Birth Cohort Study (n=5914). Early-life SES showed significant and graded associations with CRP levels at age 23 independently of later SES. For example, men with higher family income at birth showed higher CRP levels at age 23 (p=0.001 for trend) and women with less educated mothers showed higher CRP levels (p=0.01 for trend). Notably, differential directions of association between SES indicators and CRP levels between men and women were found. When adjusted for SES at age 23, men with the lowest family income at birth showed 42% lower CRP levels when compared to men in the highest family income group (-42; 95% CI: -60,-16). In contrast women born to the least educated mothers had the highest CRP levels (35; 95% CI -2, 86). In both sexes, adiposity accounted for the overwhelming majority of the associations between SES and CRP levels. Sex and gender roles specific to middle-income countries, socio-cultural and environmental conditions that may impact adiposity, and the level of epidemiological transition may be key factors that are linked to the associations between lifecourse SES and CRP levels. Public health strategies aimed at decreasing the burden of cardiovascular disease in middle-income settings, in addition to highlighting the risks associated with adult obesity, should not overlook the wide-ranging impacts of lifecourse social determinants.

Fig. 1

Proposed associations between socioeconomic indicators at birth and age 23 years with C-reactive protein (CRP) levels in young adulthood.

Fig. 2

C-reactive protein concentrations in poor vs. not poor (bottom vs. top two tertiles of family income in 2004–2005) men and women with ≤4 or >4 years of education. P-values for interaction in men = 0.001, in women = 0.6.