Even among older adults, a healthy lifestyle, one that includes physical
activity, healthy dietary habits, smoking cessation, and light or moderate
alcohol use, is associated with a significantly lower incidence of new-onset
diabetes mellitus. Researchers showed that 80% of new cases of diabetes are
attributable to these risk factors, a number that increases when obesity is
included as a risk factor.

"Our findings suggest that, even later in life, the great majority of cases of
diabetes are related to lifestyle factors," write Dariush Mozaffarian (Brigham
and Women's Hospital, Boston, MA) and colleagues in the April 28, 2009 issue of
the Archives of Internal Medicine. "Our results support the need for emphasizing
healthy and achievable physical activity and dietary goals among older adults,
including moderate leisure-time activity and walking pace, higher intake of
dietary fiber and polyunsaturated fat, and lower intake of trans fat and easily
digestible carbohydrates."

Previous studies, including a secondary analysis of the Diabetes Prevention
Program trial, have shown that structured dietary advice and physical activity
were most effective at reducing the risk of diabetes among the oldest
participants. However, as the investigators point out, that trial included
mostly high-risk patients participating in a highly structured intervention.
Other studies have shown that certain lifestyle behaviors can lower the risk of
diabetes, but these often looked at each lifestyle factor individually.

In this analysis of the Cardiovascular Health Study, Mozaffarian and colleagues
investigated the relationship between lifestyle risk factors, evaluated in
combination, and the incidence of diabetes over a 10-year period in 4883 men and
women 65 years of age and older. The group defined optimal lifestyle
characteristics and compared these low-risk behaviors with the risk of incident
diabetes mellitus.

Low-risk lifestyle behaviors were defined by physical-activity levels above the
median and never smoking or smoking <5 pack-years or having quit >20 years ago.
Alcohol use in this cohort was rare, with 94% consuming less than two drinks
daily. Individuals were also assigned a dietary score based on their intake of
dietary fiber, low glycemic index foods, lower trans fats, and a higher
polyunsaturated-to-saturated-fat ratio. Assessments of adiposity were also
performed, with a low-risk body-mass index (BMI) defined as not being
overweight, or a BMI <25, while a low-risk waist circumference for men was <92
cm and <88 cm for women.

Basic lifestyle risk factors, according to the researchers, strongly predicted
diabetes incidence, with individuals cutting their risk in half when they were
physically active and had good dietary habits. Overall, the risk of diabetes was
80% lower among individuals with physical-activity levels above the median,
healthy dietary and smoking habits, and moderate alcohol use. When healthy BMIs
and waist circumference were added to the model, the risk of new diabetes was
reduced by 89%.

If these associations are causal, "eight in 10 new cases of diabetes might have
been prevented if all older adults were in the low-risk group for these
lifestyle factors," write Mozaffarian and colleagues. When not being overweight
or not having a large waist circumference was considered as a risk factor in
addition to these other lifestyle behaviors, the number of possible prevented
cases attributable to lifestyle factors would rise to nine in 10.

"The 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 population," write the researchers.