C-reactive protein and physical activity Statistical analysis Complex analysis of the sample survey was per- formed using the SPSS software for Windows (ver- sion 17) (Chicago, IL, USA). Data were weighted for sex, age, and residential area (urban/rural) strata, ac- cording to the population of Iran (national census, 2006). Kolmogorov Smirnov analysis was employed to study the normality of variables. CRP concentra- tions in serum were log-transformed to change the distribution to normal; the log-transformed values of CRP were used in analyses. Continuous variables were expressed as mean±standard error of mean (SEM). Partial correlation coefficients were calculat- ed between quantitative CRP and features of physi- cal activity after adjustment for various variables. The adjusted values of quantitative CRP were com- pared between the categories of physical activity, using the general linear modelling method. The p value of <0.05 was considered significant. RESULTS After excluding the participants with missing data in laboratory results (n=396), analyses were per- formed for the remaining 3,001 individuals. The demographic data (age, sex, and residential area) of the excluded subjects were not different from the remaining participants. Table 1 shows the baseline characteristics of the study participants. Forty-six percent of men were in the category of high physi- Characteristics Age (year)* Area of residence Urban (%) Rural (%) BMI (kg/m2)* Waist-circumference (cm)* Physical activity category Low (%) Moderate (%) High (%) Total physical activity (MET-min/day) Duration of vigorous activity (min/day) Duration of moderate activity (min/day) Duration of sedentary behaviours (min/day) Current smoking (%±SE) Diabetes mellitus Quantitative CRP (mg/L)* Table 1. Characteristics of study participants (SuRFNCD-2007, Iran) Esteghamati A et al. cal activity while 40% of women fell into the cate- gory of low physical activity. There was no signifi- cant difference in the serum CRP levels between men and women. The serum CRP levels correlated with age (r=0.058, p=0.024 in men and r=0.065, p=0.44 in women), BMI (r=0.029, p=0.026 in men and r=0.030, p=0.023 in women), and waist-circumference (r=0.59, p=0.021 in men and r=0.047, p=0.046 in women). Current smokers had higher levels of quantitative CRP vs ex-smokers or never-smokers (5.64±3.06 vs 5.19±2.73, p=0.139 in men and 5.60±2.68 vs 5.41±2.93, p=0.69 in women). TPA was inversely associated with age (r=-0.212, p=p.002 in men and r=-0.173, p=0.005 in women), BMI (r=-0.338, p<0.001 in men and r=-0.198, p=0.001 in wom- en), and waist-circumference (r=-0.357, p<0.001 in men and r=-0.239, p<0.001 in women). CRP significantly correlated with TPA (r=-0.103, p=0.021 in men and r=-0.114, p=0.017 in wom- en), duration of vigorous-intensity activity (r=- 0.122, p=0.019 in men and r=-0.109, p=0.026 in women), duration of moderate-intensity activity (r=-0.107, p=0.031 in men and r=-0.118, p=0.020 in women), and duration of sedentary behaviours (r=0.092, p=0.029 in men and r=0.101, p=0.022 in women) after multiple adjustments for age, area of residence, BMI, waist-circumference, smoking, and diabetes mellitus using partial correlation (Table 2). Male (n=1,494) 39.42±0.75 1,011 (67.7) 483 (32.3) 25.4±0.2 88.6±0.4 31.6±1.1 22.3±0.1 46.1±1.3 909.2±47.3 58.1±5.7 111.1±4.4 240.2±4.2 26.1±1.6 6.6±0.4 5.6±0.1 Female (n=1,507) 39.76±0.78 1,004 (66.6) 503 (33.4) 27.6±0.2 88.8±0.6 48.6±1.3 27.1±1.2 24.3±1.2 327.9±13.8 4.9±0.9 72.2±2.3 238.0±4.6 1.8±0.3 9.1±0.4 5.6±0.1 Total (n=3,001) 39.59±0.54 2,015 (67.1) 986 (32.9) 26.5±0.2 88.7±0.4 40.0±1.0 24.7±0.8 35.4±1.1 623.2±31.9 31.9±3.9 91.9±3.2 239.2±3.8 14.1±1.1 7.8±0.4 5.6±0.1 Variables, except age, sex, and area of residence, were standardized for age, sex, and residential area of the 2006 population of Iran. *Mean±SE; BMI=Body mass index; CRP=C-reactive protein; MET=Metabolic equivalent; min=Minute; SE=Standard error 68 JHPN