Epidemiology of walking and type 2 diabetes

Purpose: Diabetes is prevalent, deadly, serious, and costly. It affects an estimated 20.8 million Americans ill 2005, having doubled from 1980, and is expected to reach at least 29 million by 2050. In 2002, diabetes was responsible for all estimated $132 billion in costs. Diabetes concerns leaders in public health and clinicians, and its personal, social, and economic burdens require preventive efforts such as the promotion of walking. As such, we reviewed the limited epidemiologic data of walking and incident diabetes (two studies) and walking and mortality outcomes among diabetic persons (three studies). Methods: We abstracted information from each paper to identify characteristics of the study population, details of the disease outcomes (diabetes incidence, mortality outcomes, or cardiovascular disease events among persons with diabetes), relative risks, risk reductions, and adjustment for covariates. Results: The reviewed studies were adjusted for important covariates such as age, body mass index, the coexistence of other nonwalking and vigorous activities, and so on and for biases such as differential misclassification of exposure. The strength of the observed reductions in risk were between approximately 20% and 40% for incident diabetes and between 40% and 55% for mortality due to all causes and due to cardiovascular disease (and related nonfatal events). Moderate to faster pace of walking seemed to enhance risk reduction. These reductions fit well with results of earlier reviews of physical activity and diabetes, and basically corresponded to 2-3 h of weekly walking. Conclusion: Available dose-response data between walking and the aforementioned outcomes suggest that public health recommendations for physical activity might also apply to walking in particular. Regardless, important areas remain for future research on walking and diabetes.