Sex-specific associations of childhood socioeconomic position and trajectories of metabolic traits across early life: prospective cohort study

Background Socioeconomic inequalities in cardiovascular disease risk begin early in life and are more pronounced in females compared with males in later life but the causal atherogenic traits that may explain this are not well understood. We explored sex-specific associations between indicators of childhood socioeconomic position (SEP) and changes in molecular measures of systemic metabolism across early life. Methods Data were from offspring of the Avon Longitudinal Study of Parents and Children (ALSPAC), born in 1991/1992. Maternal education was the primary indicator of SEP with paternal education and household social class used as secondary indicators; all measures were collected through questionnaires administered to mothers at 32-weeks’ gestation of the offspring pregnancy. Concentrations of 148 metabolic traits were measured using nuclear magnetic resonance spectroscopy performed on plasma samples at ages 7 years (y), 15y, 18y and 25y among offspring. The sex-specific slope index of inequality (SII) in trajectories of metabolic traits across these ages was estimated using multilevel models. Results Between 6,010-6,537 participants with 10,055-12,543 repeated measures of metabolic traits from 7y to 25y were included. Lower maternal education was associated with more adverse levels of several atherogenic lipids and other key metabolic traits among females at age 7y, but not males. For instance, the SII for very small very-low-density lipoprotein (VLDL) concentrations was 0.16 SD (95% CI: 0.01, 0.30) among females and -0.02 SD (95% CI: -0.16, 0.13) among males at 7y. Between 7y and 25y, inequalities widened among females and emerged among males particularly for VLDL particle concentrations, plasma apolipoprotein B concentrations and inflammatory glycoprotein acetyls. For instance, at 25y the SII for very small VLDL concentrations was 0.36 SD (95% CI: 0.20, 0.52) and 0.22 SD (95% CI: 0.04, 0.40) among females and males respectively. Findings for secondary SEP indicators were broadly similar although associations of paternal education with key metabolic traits were weak and less consistent among males at 25y compared with associations of maternal education. Conclusion Socioeconomic inequalities in causal atherogenic lipids and other key metabolic traits such as markers of inflammation begin in childhood and strengthen in adolescence among females but only emerge in adolescence among males, leading to wider socioeconomic inequalities among females compared with males by 25y. Prevention of socioeconomic inequalities in cardiovascular disease risk requires a life course approach that begins at the earliest opportunity in the life course especially among females.