LEMASTER, J. W., G. REIBER, D. G. SMITH, P. HEAGERTY, and C. WALLACE. Daily Weight-Bearing Activity Does Not Increase the Risk of Diabetic Foot Ulcers. Med. Sci. Sports Exerc., Vol. 35, No. 7, pp. 1093-1099, 2003.
Purpose: This study had two purposes: to identify characteristics associated with participants' usual weight-bearing activity, and to determine whether weight-bearing activity increased the risk of foot ulcer among persons with diabetes and prior foot ulcer.
Methods: We conducted a prospective cohort study of 400 participants with diabetes and a prior history of foot ulcer. Participants were from the Veterans Affairs Puget Sound Health Care System and Group Health Cooperative in Seattle, WA, and were originally assembled for a randomized controlled trial of footwear. Feet were examined and demographic and health history information was collected at enrollment. Daily weight-bearing activity was reported at enrollment and every 17 wk thereafter for 2 yr. All incident foot lesions were recorded.
Results: Weight-bearing activity was significantly higher among women. Activity was lower among participants who were older, unmarried, or who had a history of congestive heart failure, respiratory disease, stroke, or depression. Activity decreased significantly over the study period but remained similar in those with or without insensate feet. After adjustment for foot-related and health-status characteristics, moderately active participants (4.5-7.4 weight-bearing h·d-1) were at substantially but nonsignificantly reduced risk of foot ulcer compared with least active participants (<4.5 weight-bearing h·d-1) (OR 0.50, 95% CI 0.22-1.16). Most active participants (≥7.5 weight-bearing h·d-1) were at significantly reduced risk (OR 0.20, 95% CI 0.04-0.87). Weight-bearing activity exerted similar effects on foot ulcer risk in participants with insensate versus sensate feet.
Conclusion: Increased weight-bearing activity did not increase the risk of foot re-ulceration. Further studies are needed to explore weight-bearing activities that are safe for those with diabetes and insensate feet.
Foot ulcers are an important cause of morbidity and high medical costs in people with diabetes, and have been called one of the easiest long-term complications of diabetes to detect in a primary care setting (6). Among the 17 million people with diabetes mellitus in the United States, up to 15% will develop a foot ulcer in their lifetime, and approximately 15% of those individuals will require amputation (18). Attributable medical costs for a 45- to 65-yr-old male with a new foot ulcer are nearly $28,000 over 2 yr (22). Foot ulcers have been identified in the causal pathway in 84% of lower-limb amputations (19).
The role of daily weight-bearing physical activity in the development of foot ulcers among people with diabetes mellitus and insensate feet is still poorly understood. A recent National Health Interview Study estimated that 36-40% of people with diabetes have insensate feet due to diabetic peripheral neuropathy (9). People with diabetes and insensate feet experience minor trauma and increased plantar pressures, putting them at increased risk for subsequent foot ulcer (5,12,20,21,26). In a UK-based cohort study of people with diabetes, Veves and colleagues (26) found that plantar foot ulcers developed after an average of 30 months of follow-up in only 35% of those with initially elevated plantar foot pressures (93% of whom had insensate feet). These findings led to the suggestion that an increased pressure load on the insensate foot may increase foot-ulcer risk even more in patients with an active lifestyle (25). The American Diabetes Association (ADA) recommends that people with diabetes mellitus and insensate feet should limit weight-bearing activity to decrease the risk of foot ulcers (4). The American College of Sports Medicine (ACSM) recommends for people with type 2 diabetes that nonweight bearing activities should be performed by persons with peripheral neuropathy in order to mitigate irritation and/or trauma to the lower legs and feet (3). Longitudinal observational studies and controlled trials have not been reported that definitely link weight-bearing activity to increased risk of foot ulcer.
An active lifestyle has been shown to be of great benefit to persons with diabetes. Mortality rates are lower in fit persons with diabetes: after adjustment for age, measures of glycemic control, cholesterol level, body mass index (BMI), blood pressure, and family history of cardiovascular disease, all-cause (14,27) and cardiovascular mortality (24) is lower in active type 2 diabetes patients. Even when activity does not enhance aerobic fitness, it can be beneficial: Glass and colleagues (10) found in a 13-yr observational study that all-cause mortality decreased among active elderly adults with and without diabetes, even when their participants' activity did not enhance fitness. ACSM recommends that all persons with type 2 diabetes should participate in at least five 30-min sessions per week of low- to moderate-intensity physical activity (i.e., achieving 40-70% of maximal oxygen consumption) (3).
If health providers are to counsel patients with diabetes and insensate feet regarding their daily activity, it is vital that providers better understand the relationship between weight-bearing activity and the risk of foot ulcer. To investigate this issue, we conducted a 2-yr cohort study of 400 people with diabetes mellitus and a prior history of foot ulcer (23). This study had two aims: to identify characteristics associated with participants' usual daily weight-bearing activity, and to determine whether weight-bearing activity increased the risk of foot ulcer. The study hypothesized that an increase in weight-bearing activity would not increase the risk of foot ulcer, even in participants with diabetes and insensate feet.