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Title: Lifestyle factors and risk for new-onset diabetes. A population-based cohort study

Authors: J Reis, C Loria, P Sorlie, Y Park, et al

Reference: Ann Intern Med 2011; 155:292-299
http://bit.ly/uqv66J

Reviewer: Robert Goldberg, PhD, Contributing editor, ProCor; Professor of Medicine and Epidemiology, Division of Cardiovascular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA

Reviewer comments: Diabetes is an increasingly prevalent chronic condition that is associated with significant morbidity and mortality and limitations in health-related quality of life. A number of lifestyle practices, including sedentary activity, consumption of an unhealthy diet high in calories, total and saturated fats, excessive alcohol intake, and a less than optimal weight profile have been associated with an increased risk of diabetes. Using data from a large population-based cohort study of middle-aged men and women, the results of the present study suggest that a number of positive lifestyle factors can individually, and collectively, exert a significant protective effect on the risk of developing diabetes.

The results of this large prospective study in more than 200,000 men and women without previously diagnosed diabetes suggest that persons with single, and multiple, low levels of various modifiable risk factors for diabetes and CVD, including physical inactivity, smoking status, alcohol intake, and elevated BMI, were at considerably lower risk for developing diabetes than persons in higher risk categories for each of these factors. For example, men and women with a normal BMI were at an approximate three quarters lower risk for developing diabetes than heavier individuals whereas men and women who were engaged in regular physical activity were at a one quarter lower odds for developing diabetes than more sedentary individuals. Importantly, these lifestyle factors had an additive effect on the risk for developing diabetes over the nearly 11-year period of follow-up.

The present results suggest that not smoking, consuming alcohol in moderate amounts and having a heart healthy diet, participating in regular physical activity, and most importantly, maintaining optimal body weight, can pay considerable dividends with regards to preventing the onset of diabetes in middle-aged men and women. Purpose of study: To examine how individual modifiable risk factors, and combinations of various lifestyle practices, are related to the development of newly diagnosed diabetes over an 11-year follow-up period

Location of study: United States

Study design: Prospective cohort

Results: Data from the NIH-AARP Diet and Health Study cohort were utilized for the present study. Cohort participants included more than one half million members of AARP, age 50-71 years in the mid-1990's, who were enrolled from six states and two large metropolitan areas (Atlanta and Detroit).

All study participants completed a comprehensive dietary survey at the time of baseline enrollment and a brief survey about their demographic, lifestyle, and medical history characteristics; two additional questionnaire surveys were mailed to surviving participants to update their exposure to various pre-disposing factors and whether they had developed various chronic conditions, including diabetes, over the interim period. The modifiable lifestyle factors of interest included diet, use of alcohol, BMI, cigarette smoking, and participation in regular physical activity. Several of these lifestyle factors were further classified as being present or absent and low risk categories were created for the diet, smoking, and physical activity variables. For example, a dietary score was calculated based on the intake of polyunsaturated and saturated fats, fiber, and the glycemic index of various foods. Similarly, a variable of moderate alcohol consumption was constructed for men and women, optimal weight was defined as a BMI of between 18.5 and 24.9 kg/m2 and not smoking was defined as being at low risk for the smoking status variable. Low risk physical activity was defined as participation in at least 20 minutes of physical activity three or more times per week.

A total of nearly 115,000 men, and slightly more than 92,000 women, without evidence of CHD, cancer, or diabetes, at the time of baseline enrollment were included in the present investigation. The average age of study participants was approximately 61 years and the majority of cohort enrollees were white; nearly one third of cohort enrollees had two of the examined lifestyle factors in the low-risk category. Over the course of follow-up, 11,031 men and 6969 women developed new onset diabetes; this amounted to approximately one in every 10 men and one in every 14 women.

Each of the examined positive lifestyle factors was associated with a reduced risk for diabetes, particularly an elevated BMI. For example, compared to persons with a BMI greater than 25 at the time of baseline enrollment, the odds of developing diabetes were 70% lower for men and 78% lower for women who were of normal body weight. Similarly, the multivariable adjusted odds ratios ranged from 0.76 to 0.85 for men, and from 0.63 to 0.84 for women, for each of the other modifiable risk factors examined, reflecting lower risks of developing diabetes ranging from a low of 16% to upwards of 37%.

Men appeared to particularly benefit from not smoking than women whereas women seemed to benefit from a lower BMI and moderate alcohol consumption than men.

In examining the association between various combinations of these factors and the odds for developing diabetes, considerable health benefits were noted for those with multiple low levels of these risk factors. Men and women with both "low risk" physical activity and a diet score in the low-risk category, had an approximately 29% lower odds for developing diabetes, after adjustment for the three other lifestyle factors of smoking, physical activity, and moderate alcohol consumption. Similarly, being in the low risk of categories for diet, physical activity, and not smoking was associated with a one-third lower odds for diabetes in men and women. Men and women who were at low risk for these previously mentioned factors, and consumed moderate amounts of alcohol, had a 39% and 57% lower odds for developing diabetes, respectively. Finally, men and women with all of the examined factors in the low-risk category, which unfortunately represented 4% of all men and 2% of all women, had a 72% and 84% lower odds for developing diabetes, respectively.