Lifecourse infectious origins of sexual inequalities in central adiposity.

Background: Social disparities in obesity are often more marked among women than men, possibly due to social factors. Taking a life-history perspective, we hypothesized that childhood infections could be relevant via sex-specific effects of immune system activation on sexual development and, hence, body shape.

Methods: We used multivariable linear regression to assess the sex-specific, adjusted associations of 'childhood' pathogens [0 (n = 1002), 1 (n = 2199), 2 (n = 3442) or 3 (n = 4833) of HSV1, CMV and hepatitis A antibodies] and 'adult' pathogens [0 (n = 5836), 1 (n = 3018) or ≥ 2 (n = 720) of HSV2, HHV8 and hepatitis B or C) with waist-hip ratio (WHR) and body mass index (BMI) standard deviations (SDs) using NHANES III (1988-94). As validation, we assessed associations with height.

Results: 'Childhood' pathogens were positively associated with WHR among women [0.18 SD, 95% confidence interval (95% CI) 0.04-0.32 for 3, compared with 0], but not men (-0.04 SD, 95% CI -0.15 to 0.08), adjusted for age, education, race/ethnicity, smoking and alcohol. Further adjustments for leg length barely changed the estimates. There were no such sex-specific associations for BMI or for adult pathogens. 'Childhood', but not 'adult', pathogens were negatively associated with height, adjusted for age, sex, education and race/ethnicity.

Conclusions: These observations are consistent with the lifecourse hypothesis that early exposure to infections makes women vulnerable to central obesity. This hypothesis potentially sheds new light on the developmental origins of obesity, and is consistent with the generally higher levels of central obesity among women than men in developing populations.