Published: Apr 2, 2014 | Updated: Apr 3, 2014
By Nancy Walsh, Senior Staff Writer, MedPage Today

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A 6-year lifestyle intervention decreased the incidence of diabetes, cardiovascular mortality, and all-cause mortality in adults with impaired glucose tolerance, a Chinese study found.

During 23 years of follow-up, individuals in the intervention group had a 45% lower risk of developing diabetes (HR 0.55, 95% CI 0.40-0.76, P=0.001) than those who did not take part in the intervention, according to Guangwei Li, MD, of China-Japan Friendship Hospital in Beijing, and colleagues.

In addition, they had a 41% decrease in cardiovascular mortality (HR 0.59, 95% CI 0.36-0.96,P=0.033) and a 29% decrease in all-cause mortality (HR 0.71, 95% CI 0.51-0.99, P=0.049), the researchers reported online in The Lancet Diabetes & Endocrinology.

In an accompanying commentary, Nicholas J. Wareham, MBBS, PhD, of the University of Cambridge in England described these findings as “a real breakthrough, showing that lifestyle intervention can reduce the risk of long-term cardiovascular consequences of diabetes.”

Diet and exercise interventions for patients with impaired glucose tolerance have been shown to prevent or delay the onset of diabetes and to decrease the risk for other cardiovascular problems over the short term.

However, whether these improvements can translate into long-term benefits including in mortality has been unclear.

To explore the issue the Da Qing Diabetes Prevention Study, beginning in 1986, enrolled 577 patients from 33 clinics in a cluster randomized trial.

In a previous analysis of this cohort, Li and colleagues found only a nonsignificant decrease of 17% in mortality from cardiovascular causes and a 47% lower incidence of severe, vision-threatening retinopathy (HR 0.53, 95% CI 0.29-0.99, P=0.048) over 20 years of follow-up.

To provide further long-term data, particularly for mortality, they have now analyzed data from an additional 3 years. At baseline, the clinics were randomized so that their patients received a diet-only intervention, an exercise-only intervention, both diet and exercise, or standard medical care without a specific lifestyle program.

For the purposes of statistical analysis, the investigators determined a priori to combine the intervention groups to improve their power to detect an attributable difference in mortality.

During the 23-year follow-up, there were 174 deaths, with 121 being in the combined intervention group. Complete mortality data were available for 94% of participants.

The cumulative incidence of death from any cause in the intervention group was 28.1% (95% CI 23.9-32.4), compared with 38.4% (95% CI 30.3-46.5) among controls receiving routine medical care only.

A total of 51 patients in the intervention group died of cardiovascular causes, as did 27 controls, for cumulative incidences of 11.9% (95% CI 8.8-15) and 19.6% (95% CI 12.9-26.3), respectively.

The cumulative incidence of diabetes reached 72.6% (95% CI 68.4-76.8) among patients participating in the lifestyle intervention compared with 89.9% (95% CI 84.9-94.9) among those in the standard care group.

Marked differences were seen in mortality according to gender, with hazard ratios of 0.46 (95% CI 0.24-0.87, P=0.02) for all-cause mortality and 0.28 (95% CI 0.11-0.71, P=0.01) for cardiovascular mortality among women, but no significant decreases in either cause of death for men.

Li’s group suggested that men may have been less adherent to the lifestyle program, and that there may have been other potential confounders contributing to the differences in mortality.

“We have been unable to establish any definitive reasons for differences in the effect of the intervention on mortality between men and women,” they stated.

The researchers also determined that longer time until the development of diabetes was associated with reduced all-cause and cardiovascular mortality.

“After inclusion of time to onset of diabetes in the multivariable models the intervention variable was no longer statistically significant, suggesting that the reduction in mortality associated with the intervention is mediated by its effect in delaying the onset of diabetes,” they wrote.

“This study is the first to show that lifestyle intervention in people with impaired glucose tolerance can both reduce the incidence of diabetes and decrease mortality, and so it has important implications for public health policy about diabetes prevention in China and worldwide,” the investigators wrote.

In Wareham’s comment, he wrote of the study, “The quality and completeness of follow-up information is exemplary and a testament to the strong teamwork of the research groups involved.”

“The lesson from the Da Qing Prevention Study is that such long-term studies have scientific value, but the challenge is to match the excellent completeness of follow-up achieved in this study in an equally efficient manner in other trials,” he stated.

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