Systematic review of active commuting to school and childrens physical activity and weight.

BACKGROUND: The recent decline in children's active commuting (walking or biking) to school has become an important public health issue. Recent programs have promoted the positive effects of active commuting on physical activity (PA) and overweight. However, the evidence supporting such interventions among schoolchildren has not been previously evaluated. METHODS: This article presents the results of a systematic review of the association between active commuting to school and outcomes of PA, weight, and obesity in children. RESULTS: We found 32 studies that assessed the association between active commuting to school and PA or weight in children. Most studies assessing PA outcomes found a positive association between active commuting and overall PA levels. However, almost all studies were cross-sectional in design and did not indicate whether active commuting leads to increased PA or whether active children are simply more likely to walk. Only 3 of 18 studies examining weight found consistent results, suggesting that there might be no association between active commuting and reduced weight or body mass index. CONCLUSION: Although there are consistent findings from cross-sectional studies associating active commuting with increased total PA, interventional studies are needed to help determine causation.

Physical activity and cancer prevention: etiologic evidence and biological mechanisms.

Scientific evidence is accumulating on physical activity as a means for the primary prevention of cancer. Nearly 170 observational epidemiologic studies of physical activity and cancer risk at a number of specific cancer sites have been conducted. The evidence for decreased risk with increased physical activity is classified as convincing for breast and colon cancers, probable for prostate cancer, possible for lung and endometrial cancers and insufficient for cancers at all other sites. Despite the large number of studies conducted on physical activity and cancer, most have been hampered by incomplete assessment of physical activity and a lack of full examination of effect modification and confounding. Several plausible hypothesized biological mechanisms exist for the association between physical activity and cancer, including changes in endogenous sexual and metabolic hormone levels and growth factors, decreased obesity and central adiposity and possibly changes in immune function. Weight control may play a particularly important role because links between excess weight and increased cancer risk have been established for several sites, and central adiposity has been particularly implicated in promoting metabolic conditions amenable to carcinogenesis. Based on existing evidence, some public health organizations have issued physical activity guidelines for cancer prevention, generally recommending at least 30 min of moderate-to-vigorous intensity physical activity on > or =5 d/wk. Although most research has focused on the efficacy of physical activity in cancer prevention, evidence is increasing that exercise also influences other aspects of the cancer experience, including cancer detection, coping, rehabilitation and survival after diagnosis.

Use of protective equipment among California farmers.

BACKGROUND: Agriculture is a hazardous industry associated with many occupational injuries and illnesses. We describe California farmers' self-reported exposure to five agricultural hazards and their use of protective equipment. METHODS: A telephone survey of 1,947 California farmers recorded information on occupational exposure, health outcomes and use of protective equipment to lessen risk from exposure to dust, sun, noise, pesticides and tractors. RESULTS: Over 93% of respondents reported using personal protection around pesticides; however, fewer than 1/3 used consistent protection against other hazards. Younger age and male sex were associated with better use of protection from dust, noise, pesticide and tractors, but negatively associated with sun protection. There was no consistent relationship of protective behaviors with cigarette smoking, living on the farm, marital status, or time in non-administrative farmwork. Risk perception was strongly associated with behavior; farmers concerned about specific health problems were much more likely to use protective equipment. CONCLUSIONS: Some farmer characteristics are associated with more safe behaviors, but efforts to encourage protective behaviors on farms should be broadly based in view of a lack of a single risk-taking profile among California farmers.