Diabetes Knocks Down Life Expectancy

ROTTERDAM, The Netherlands, June 12 -- Before heart disease even develops among patients with heart disease, the effects on life expectancy have already begun, found researchers here.

In an analysis of the Framingham Heart Study, diabetic men and women age 50 and older died on average 7.5 and 8.2 years earlier, respectively, than those who did not have diabetes.

This difference was accounted for by a reduction in life expectancy free of cardiovascular disease by 7.8 years for men and 8.4 years for women, said Oscar H. Franco, M.D., D.Sc., Ph.D., of the University Medical Center Rotterdam and Unilever Corporate Research in Sharnbrook, England, and colleagues.

Life expectancy with cardiovascular disease was not significantly different between groups, they reported in the June 11 issue of the Archives of Internal Medicine.

"These findings underscore the importance of diabetes prevention for the promotion of healthy aging," they wrote.

The results also confirm the lower life expectancy for diabetic patients seen in the National Health and Examination Survey (NHANES I) and estimates from the National Health Interview Surveys (NHIS), although both of these studies had shorter follow-up and did not look at years lived with and without cardiovascular disease.

Dr. Franco and colleagues built life tables using data from the Framingham Heart study. That study included 5,209 residents of Framingham, Mass., ages 28 to 62 who were examined biannually for more than 46 years.

In the current analysis, the researchers calculated life expectancy only for participants who were 50 or older. Those with cardiovascular disease at baseline or who had missing data on potential confounders were excluded.

Cardiovascular disease was defined as encompassing coronary heart disease (including MI), heart failure, stroke, transient ischemic attack, and intermittent claudication. All events were adjudicated by a panel of three physicians.

The total life expectancy at age 50 for women was 26.5 years for those who had diabetes and 34.7 years for those who did not have the disease. Most of the difference was accounted for in life expectancy free of cardiovascular disease (19.6 versus 28.0 years).

The difference in life expectancy with cardiovascular disease between those who had diabetes and those who didn't was an insignificant 0.2 years (6.6 versus 6.8 years).

For men, the total life expectancy was 21.3 years for those who had diabetes and 28.8 years for those who did not have the disease. Again, life expectancy with cardiovascular disease was similar between groups (7.1 versus 6.8 years), whereas life expectancy free of cardiovascular disease was shorter for those with diabetes (14.2 versus 22.0 years).

As expected, the risk of developing cardiovascular disease and mortality was significantly elevated with diabetes. After adjustment for age and confounding variables, the hazard ratios were:

• Incident cardiovascular disease risk was more than twice as common in patients with diabetes than in those who did not have the disease (HR 2.27 for men and 2.34 for women, P<0.05 for both).
• Mortality risk among those with cardiovascular disease was significantly elevated in the presence of diabetes (HR 1.66 for men and 2.16 for women, P<0.05 for both).
• Mortality risk among those without cardiovascular disease was elevated in the presence of diabetes but not significantly so (HR 1.26 for men and 1.31 for women).

The gender difference in the effect of diabetes on morbidity and mortality could be caused by several mechanisms, Dr. Franco and colleagues said.

Diabetes may contribute more to conventional risk factors for women than men, they said. Women may also be less likely to receive diabetes treatment and get less pharmacologic treatment for cardiovascular disease prevention, they noted.

The disadvantage for women may be even greater now, given that some of the data under study were from the 1950s, '60s, and '70s, before statins were available and when hypertension treatment was "well below current standards," the researchers said.

The overall life expectancy findings may also be of limited generalizability to the current population, they added.

While "great advances in health promotion and in the diagnosis, prevention, and treatment of cardiovascular disease have occurred since the Framingham Health Study started," they wrote, "? the incidence of diabetes has largely increased in recent years owing to detrimental changes in lifestyle."

Therefore, they said, it is essential to implement strategies for improved diet and physical activity for the general population.

"Prevention of diabetes is a fundamental task facing today's society, with the aim to achieve populations living longer and healthier lives," they concluded.