Body mass index and infectious disease mortality in midlife in a cohort of 2.3 million adolescents.

BACKGROUND: Obesity was linked to altered immunity, but also to favorable outcomes among patients with infectious disease (ID) in some settings. We assessed the association between adolescent body mass index (BMI) and ID mortality.

METHODS: BMI of 2 294 139 Israeli adolescents (60% men; age 17.4±0.3 years) was measured between 1967 and 2010. The outcome, obtained by linkage with official national records, was death due to ID as the underlying cause. Multivariable Cox proportional hazards models were applied.

RESULTS: During 42 297 007 person-years of follow-up (median 18.4 years), there were 689 deaths from ID (mean age 44.1±10.5 years). Adjusted hazard ratios (HR) were 1.039 (1.011-1.068) and 1.146 (1.099-1.194) among men and women, respectively, per unit increment in BMI (P for sex interaction=4.4 × 10-5 ). Adjusted hazard ratios among men were 1.2 (1.0-1.5), 1.9 (1.4-2.5) and 2.5 (1.5-4.2) for those with high-normal BMI (22.0-24.9 kg m-2 ), overweight and obese, respectively, compared with the 18.5⩽BMI<22 kg m-2 reference group, and 1.7 (1.1-2.6), 2.6 (1.6-4.3) and 6.6 (3.3-13.1) among women, respectively. The increased risk among underweight (<18.5 kg m-2 ) boys was attenuated when the study sample was restricted to those with unimpaired health at baseline. A multivariable spline model indicated a minimum risk for total ID mortality at 20.7 and 18.0 kg m-2 for men and women, respectively, with significantly increased risk seen above adolescent BMI values of 23.6 and 24.0 kg m-2 , respectively. The association with BMI was particularly evident for bacterial infections (predominantly sepsis), airways and central nervous system infections (63% of the ID deaths).

CONCLUSIONS: Adolescent overweight and obesity were strongly associated with ID mortality, especially of bacterial origin and among women.