Cardiorespiratory fitness, sedentary time, and cardiovascular risk factor clustering

Purpose Prolonged sedentary time (ST) is associated with cardiovascular risk factors (CV-RF) independent of physical activity (PA). Whether a high level of cardiorespiratory fitness (CRF) can modify the deleterious health consequences related to high ST is not known. Methods We performed a cross-sectional study of 12,274 men and 14,209 women (≥20 yr) without known cardiovascular disease. Self-reported ST measurements during a regular day were divided into three sex-specific equally sized groups (≤4, 5 to <7, and ≥7 h·d^-1). CRF was estimated (eCRF) using a previously validated nonexercise model. Using logistic regression analyses, adjusted odds ratios (OR) and 95% confidence intervals (CI) were estimated for the association of ST with CV-RF clustering and for the potential modifying effect of eCRF. Results Each hour increase in ST was associated with 5% and 4% greater likelihood of having CV-RF clustering independent of PA in men and women, respectively. Among the participants with higher levels of eCRF, the adjusted OR values associated with ≥7 h·d^-1 of ST were 0.92 (0.56-1.51) for men and 1.16 (0.49-2.74) for women, compared with men and women with low ST (≤4 h·d^-1) and high eCRF levels. In combined analyses of eCRF, PA, and ST, compared with the reference group of participants meeting the recommendations, ≤4 h·d^-1 of ST and high eCRF, the OR values were 0.63 (0.27-1.44) and 0.65 (0.14-3.07) in fit men and women with ≥7 h·d^-1 of ST, which did not meet the recommendations. Men and women meeting the PA recommendations, but were unfit, had significantly increased odds of having CV-RF clustering across levels of ST. Conclusion High levels of eCRF abolished the increased odds of having CV-RF clustering associated with high ST, even among those individuals who did not meet the current PA recommendations.