Overall , the current literature supports clearly the dose-response relationship between physical activity and the seven chronic conditions identified .
Moreover , higher levels of physical activity reduce the risk for premature all-cause mortality .
The current Canadian guidelines appear to be appropriate to reduce the risk for the seven chronic conditions identified above and all-cause mortality
This systematic review examines critically the scientific basis for Canada 's Physical Activity Guide for Healthy Active Living for adults .
Particular reference is given to the dose-response relationship between physical activity and premature all-cause mortality and seven chronic diseases ( cardiovascular disease , stroke , hypertension , colon cancer , breast cancer , type 2 diabetes ( diabetes mellitus ) and osteoporosis ) .
The strength of the relationship between physical activity and specific health outcomes is evaluated critically .
Physical activity in different periods of life and the risk of breast cancer: the Norwegian-Swedish Women's Lifestyle and Health cohort study.
BACKGROUND Physical activity has been found to be associated with decreased risk of breast cancer in postmenopausal women in the majority of epidemiologic studies , but the association is inconsistent in premenopausal women . METHODS We studied the effect of physical activity at various ages on the incidence of breast cancer in 99,504 women from 30 to 49 years of age at enrollment in the Women 's Lifestyle and Health Study , a prospect i ve population -based cohort study in Norway and Sweden .  Physical activity level on an ordinal scale at age 14 , age 30 , and age at enrollment , participation in competitive sports , as well as information on other covariates was obtained using a self-administered question naire . Complete follow-up with data on incident invasive breast cancer and mortality was collected by linkage to national registries . The relation between physical activity  and time to breast cancer development was assessed using Cox proportional hazard models , controlling for potential confounders . RESULTS During an average 9.1 years of follow-up , there were 1,166 incident breast cancer cases . The mean age of the women was 41 years at enrollment , and the mean age at breast cancer diagnosis was 48 years . Compared to inactive women , women with higher levels of physical activity at enrollment had a similar risk of incident breast cancer ( adjusted relative risk , 1.24 for vigorous activity compared with no activity ; 95 % CI , 0.85 - 1.82 ) . Physical activity at age 30 or at age 14 also did not afford any significant protection from breast cancer , nor did a consistently high level of activity from younger ages to enrollment . CONCLUSIONS We did not find evidence of a protective effect of physical activity on breast cancer risk in this group of primarily premenopausal women
Overall , the current literature supports clearly the dose-response relationship between physical activity and the seven chronic conditions identified .
Moreover , higher levels of physical activity reduce the risk for premature all-cause mortality .
The current Canadian guidelines appear to be appropriate to reduce the risk for the seven chronic conditions identified above and all-cause mortality
This systematic review examines critically the scientific basis for Canada 's Physical Activity Guide for Healthy Active Living for adults .
Particular reference is given to the dose-response relationship between physical activity and premature all-cause mortality and seven chronic diseases ( cardiovascular disease , stroke , hypertension , colon cancer , breast cancer , type 2 diabetes ( diabetes mellitus ) and osteoporosis ) .
The strength of the relationship between physical activity and specific health outcomes is evaluated critically .