"Given medical challenges, health care costs, long-term complications and growing incidence and prevalence of type 2 diabetes mellitus, preventing the onset of clinical diabetes is of paramount importance," the authors write. While previous studies have found lifestyle factors such as level of physical activity, diet, smoking habits, alcohol use and body fat levels as risk factors linked to onset of diabetes in younger populations, the combined impact of these factors on risk of diabetes in older adults is largely unknown.
Dariush Mozaffarian, M.D., Dr.P.H., of Harvard School of Public Health, Brigham and Women's Hospital and Harvard Medical School, Boston, and colleagues with the Cardiovascular Health Study examined the relationships of lifestyle risk factors with incidence of diabetes during a 10-year period (1989 to 1998) among 4,883 men and women age 65 years or older. At the beginning of the study, the average participant age was 73 years, 58.6 percent were women and 11.4 percent were nonwhite; 95 percent of nonwhite participants were black. Approximately half of the participants had never smoked.
Low-risk lifestyle groups were defined by physical activity level (leisure time activity and walking pace) above the median (midpoint); dietary score (higher fiber intake and polyunsaturated to saturated fat ratio, lower trans-fat intake and lower average glycemic index); amount of smoking, if any; alcohol use (predominantly light or moderate); body mass index less than 25; and waist circumference of 34.6 inches or less for women or 36 inches or less for men.
After adjustment for age, sex, race, educational level, annual income and other lifestyle factors simultaneously, each lifestyle risk factor was independently associated with incidence of diabetes. Overall, each additional lifestyle factor an individual had in the lower-risk group was associated with a 35 percent lower risk of diabetes.
Individuals in the low-risk category for only physical activity level and dietary habits (nearly one in four adults) had a 46 percent lower incidence of diabetes. Combining low-risk groups for physical activity level, dietary habits, smoking habits and alcohol use (6 percent of participants), an 82 percent lower risk of diabetes was present, and four in five new cases of diabetes appeared to be attributable to not having these low-risk lifestyle factors. Adding either not being overweight or not having large waist circumference was associated with an 89 percent lower risk of diabetes.
"These findings provide an estimate of the public health burden of combined nonoptimal lifestyle risk factors for incidence of diabetes in older adults, the fastest growing segment of the U.S. population," the authors write. "Our findings suggest that, even later in life, the great majority of cases of diabetes are related to lifestyle factors."