ABSTRACT
Objective To explore the relationship between physical activity(PA) and the risk of colon cancer. Methods Cohort studies on physical activity and risk of colon cancer were identified by searching MEDLINE, EMBASE, Chinese Bio-medicine and Chinese Wanfang databases from January 1979 to December 2009. Results from the individual studies were synthetically combined in our study. Inverse variance weighting was used in fixed effects model and the random effects estimate was based on the DerSimonian-Laird method. Variance-weighted least squares method was used for trend test of summarized dose-response data. Results A total of 28 studies were included in our analysis. An inverse association between physical activities and the risk of colon cancer was observed with the relative risks (RR) as 0.75 [95% confidence interval (CI): 0.66-0.86] in males and 0.85(95%CI: 0.76-0.95)in females, respectively. However, the findings from those documents with high quality showed significant and borderline significant associations between PA and colon cancer in both males (RR=0.74, 95% CI: 0.61-0.90) and females (RR=0.99, 95% CI: 0.95-1.02). Meanwhile, the dose-response trend was not observed either in males (P=0.142) or in females (P=0.417). For men, the pooled RRs differed by subsites were 0.62(95%CI:0.45-0.85) and 0.74 (95%CI:0.56-0.99)for highest level PA, compared with lowest level PA in proximal colon and distal colon cancer,respectively. For women, the pooled RRs were 0.84 (95%CI: 0.69-1.01 ) in proximal colon and 0.75(95%CI: 0.53-1.05)in distal colon cancer, respectively. Conclusion These results added to the evidence for the protective effects in colon cancer among men and women.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the association between anthropometry and risk of breast cancer among pre-and post-menopausal women in urban Shanghai.</p><p><b>METHODS</b>A total of 73 461 female residents aged 40 to 70 years in urban Shanghai were recruited in a prospective cohort study (the Shanghai women's health study) during 1997 through 2000, and were actively followed up biennially. During mean follow-up period of 5.66 years, 432 incident cases of breast cancer were identified in the cohort. Cox regression model was used to estimate the adjusted relative risks (RRs) and 95% confidence intervals (CIs).</p><p><b>RESULTS</b>After adjustment for some potential confounding factors, baseline weight, body mass index(BMI), waist-to-hip ratio(WHR) and weight gain since age 20 were positively associated with the increased risk of breast cancer among postmenopausal women. The positive association between height and breast cancer was found among premenopausal women. Among them, those with height taller than 161 cm at age 20 experienced 1.84 fold increased risk (95% CI: 1.30-2.61) of breast cancer compared to their counterpart with height shorter than 157.1 cm. Women who were either much heavier or lighter than average at age 20 were at reduced risk. Further analyses mutually adjusted for BMI and WHR did not substantially alter the positive association for both BMI and WHR. After further adjustment for BMI, weight gain since age 20 was significantly associated to an increased risk for postmenopausal breast cancer (RR = 1.61, 95% CI: 1.09-2.37).</p><p><b>CONCLUSIONS</b>Weight gain and central obesity seemed to be strong predictors for the risk of breast cancer among postmenopausal women. Controlling weight and decreasing fat around waist were effective means to prevent postmenopausal breast cancer and height might serve as a risk factor for premenopausal breast cancer.</p>