High BMI and low cardiorespiratory fitness in adolescence are associated with increased risk of severe bacterial infections in adulthood.

Abstract

Obesity and poor physical fitness in youth are established risk factors for future cardiovascular disease and cancer. However, their potential impact on the risk of severe bacterial infections later in life remains unclear. This register-based cohort study followed almost 1 million Swedish conscripts (mean age 18.3 years) over a period of three decades. Measured body mass index (BMI) and cardiorespiratory fitness (CRF) at conscription to military service served as exposure variables, whereas outcomes included morbidity and mortality attributed to bacterial pneumonia, sepsis, and infective endocarditis. High BMI and low CRF in late adolescence were strongly associated with an increased risk of bacterial pneumonia, sepsis, and infective endocarditis in adulthood. The highest risk was seen among the obese for sepsis (hazard ratio [HR] 3.1 (2.7-3.5)), with elevated hazards observed already at high-normal BMI levels (22.5-25 kg/m²), compared with BMI 18.5-19.9. The risk of dying due to bacterial infections increased gradually with higher BMI. High, compared with low CRF, was associated with lower risk of contracting bacterial infections (0.78, 0.76-0.80), and dying from them (0.58, 0.51-0.65). High BMI and low CRF in adolescence are associated with an increased risk of contracting and dying of severe bacterial infections later in life. Hence, addressing these preventable risk factors in youths may serve as an effective measure to improve their long-term health.