Among patients in Japan with type 2 diabetes, a BMI of 18.5 to 24.9 kg/m2 appears to be associated with the lowest mortality rate, with no mortality benefit conferred by obesity, according to recent findings.
Moreover, patients in the leanest BMI category of this study were found to have increased mortality rates, the researchers wrote.
In the study, the researchers pooled data on 2,620 adults aged 40 to 70 years with type 2 diabetes enrolled in two cohorts, the Japan Diabetes Complication Study and the Japanese Elderly Diabetes Intervention Trial. In both studies, annual reports from the investigators provided anthropometric and laboratory data, clinical variables and outcome data on all patients.
The researchers defined the study’s primary endpoint as all-cause mortality, with and without exclusion of deaths that occurred within the first 4 years of follow-up. The researchers approximated hazard ratios by Cox regression, and these were adjusted for age, smoking, leisure-time physical activity and other confounding factors. Patients were stratified into BMI categories of 14.4-18.5 kg/m2 (5.2%); 18.5-22.4 kg/m2 (37.3%); 22.5-24.9 kg/m2 (31%) and 25-37.5 kg/m2 (26.6%).
The researchers found that during the 6.3 year follow-up, there were 14 deaths (10.4%) in the 14.4-18.5 kg/m2 category, 45 deaths (4.6%) in the 18.5-22.4 kg/m2 category, 38 deaths (4.7%) in the 22.5-24.9 kg/m2 category and 34 deaths (4.9%) in the 25-37.5 kg/m2 category.
There was no significant mortality trend among patients with BMI ≥18.5 kg/m2 (P for trend=.69). Conversely, the hazard ratio of individuals with BMI <18.5 kg/m2 vs. those in the 22.5-24.9 kg/m2 group was 2.58 (95% CI, 1.38-4.84). This hazard ratio decreased only slightly after adjusting for deaths in the first 4 years of follow-up.
According to the researchers, the finding regarding lean patients was particularly noteworthy, and warrants additional follow-up.
“The mechanism underlying higher mortality among lean patients is unclear,” the researchers wrote. “A potential explanation is unintentional weight loss due to chronic inflammation. …. Furthermore, inflammation may be a manifestation of comorbidities of diabetes such as cardiovascular diseases, cancer and infectious diseases.”
Disclosure: The researchers report no relevant financial disclosures.