Associations of leisure time physical activity, self-rated physical fitness, and estimated aerobic fitness with serum C-reactive protein among 3803 adults

Objective Serum C-reactive protein (CRP), a marker of systemic inflammation, is a risk factor for cardiovascular disease. Obesity and physical activity are associated with CRP, though population studies are sparse. Methods and results We assessed the cross-sectional relationship of physical activity, self-rated fitness and estimated aerobic fitness with serum CRP among a population-based random sample of 3803 Finnish adults aged 25–74 years. Conditioning, commuting and non-conditioning physical activity was measured by a recall and self-rated physical fitness by a questionnaire. A non-exercise test was used to estimate aerobic fitness. The combined association of aerobic fitness and waist-to-hip ratio (WHR) on CRP was also assessed. Self-rated fitness and aerobic fitness had inverse associations with CRP (adjusted for age, WHR, smoking, anti-hypertensive drugs, aspirin, diabetes, hypercholesterolemia, hormone replacement therapy and menopausal status) in both sexes (p < 0.001). An inverse age-adjusted association of conditioning and non-conditioning physical activity with CRP was found in both sexes. After further adjustments, associations remained significant in women for conditioning and non-conditioning activity (p < 0.001 and p = 0.010, respectively) and borderline significant in men (p = 0.074 and p = 0.070, respectively). Commuting physical activity was inversely associated with CRP among women only (p = 0.012). Conclusions Physical activity and fitness may have an anti-inflammatory effect, which is independent of obesity.