C-reactive protein and physical activity Esteghamati A et al. Fig. Serum CRP levels in different levels of physical activity, stratiﬁed according to gender 6.5 Males Females 6.0 ) /gL 5.5 m ( P R C 5.0 4.5 0 Low Moderate Physical activity categories High There was a signiﬁcant (p<0.01) association between quantitative CRP and the categories of physi- cal activity in males and females after adjustment for age, residential area, body mass index, waist-circumference, smoking, and diabetes mellitus (SuRFNCD-2007, Iran). CRP=C-reactive protein ranges of CRP. However, our findings are important because it shows that, even in a general sample of a population where most people have a normal range of CRP, the level of physical activity is an im- portant indicator, which contributes to the mild differences of CRP levels among different individu- als of the population. Our results are generally consistent with those of the growing number of studies, suggesting that high levels of physical activity are associated with lower levels of quantitative CRP (7,10). In a study which evaluated the effect of physical ac- tivity on serum CRP levels among 3,075 men and women, higher levels of exercise were associated with lower levels of quantitative CRP (11). In a co- hort of 5,888 men and women aged over 65 years, those in the highest quartile of physical activity had 19% lower concentrations of quantitative CRP compared to persons in the lowest quartile (12). In another study, physical activity was sig- nificantly and inversely associated with several in- flammatory variables, including quantitative CRP (13). They also showed that, after a 20-year follow- 70 up, the quantitative CRP levels of those who were inactive at first but later took up light physical ac- tivity reached the CRP levels of the participants who were active throughout the follow-up (13). Physical activity was independently associated with lower odds of having an elevated level of quantitative CRP in the Third National Health and Nutrition Examination Survey (14). Compared to these studies, our study has the advantage of evalu- ating the impact of different intensities of physical activity using the concept of METs. Furthermore, our study could show that this association was in- dependent of indicators of body adiposity and dia- betes. Our findings also, for the first time, point to a significant association between the time spent on sedentary behaviour and the quantitative CRP lev- els, independent of physical activity and obesity. Consistent with our findings, Fischer and col- leagues showed that the plasma levels of CRP were associated with physical inactivity, independent of obesity (24). Similarly, Tomaszewski and col- leagues showed that the circulating levels of CRP could be markedly suppressed, independent of to- tal adiposity or indeed fat mass, by intense regular JHPN