Alberta Physical Activity and Breast Cancer Prevention Trial: Inflammatory Marker Changes in a Year-long Exercise Intervention among Postmenopausal Women
Mené sur des femmes ménopausées en bonne santé de la cohorte "Alberta Physical Activity and Breast Cancer Prevention", cet essai évalue l'association entre la pratique d'exercices aérobiques d'intensité modérée ou élevée sur une période d'un an et le niveau d'expression de biomarqueurs de l'inflammation
Chronic low-grade inflammation is a possible risk factor for cancer that may be modifiable with long-term exercise. Very few randomized controlled trials (RCT) have studied the isolated effects of exercise on low-grade inflammation exclusively in postmenopausal women. The Alberta Physical Activity and Breast Cancer Prevention (ALPHA) Trial, a two-armed RCT in healthy postmenopausal women, examined how one year of moderate-to-vigorous aerobic exercise, compared to usual inactivity, influenced circulating inflammatory markers. Baseline, 6- and 12-month serum was analyzed using direct chemiluminescent immunoassays to measure high sensitivity C-reactive protein (CRP) and enzyme-linked immunosorbent assays to measure interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). Intention-to-treat analyses were performed using linear mixed models. Statistically significant differences in CRP were observed over 12 months for exercisers versus controls (treatment effect ratio = 0.87, 95% confidence interval = 0.79-0.96, P = 0.005) but not in IL-6 or TNF-α. A statistically significant trend (P-trend = 0.021) of decreasing CRP with increasing exercise adherence and stronger intervention effects on CRP in women with higher baseline physical fitness (P-heterogeneity=0.040) was found. The intervention effect on CRP became statistically non-significant with adjustment for dietary fiber intake change and seemed to be mediated by fat loss. Low-grade inflammation may be lowered with exercise, but confounding by dietary intake occurred and should be considered in future studies. Further trials are needed to corroborate our findings regarding the optimal dose of exercise required to lower CRP levels and effect modification of CRP changes by levels of body fatness and fitness.