August 15, 2017
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Lifestyle changes benefit black adults with lower diabetes risk

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Black adults at the lower end of the diabetes risk spectrum may derive greater long-term benefits when modifying several risk factors compared with those deemed to be at higher risk for the disease, according to an analysis of the Jackson Heart Study.

“Evidence on the role of modifiable risk factors among [African-Americans] is lacking,” Joshua J. Joseph, MD, assistant professor of medicine in the division of endocrinology, diabetes and metabolism at Ohio State University Wexner Medical Center, and colleagues wrote. “A key limitation of prior investigations was the inclusion of BMI in combined modifiable lifestyle risk factor metrics, which is counterintuitive as: (1) obesity may be a transient state in the pathway to diabetes and (2) the relationship between adiposity and diabetes may vary by race/ethnicity, as evidenced by stronger relationships between BMI and diabetes among [non-Hispanic whites] vs. [African-Americans].”

Joseph and colleagues analyzed data from 3,252 black adults without diabetes at baseline participating in the Jackson Heart Study, a prospective study of the development of progression of cardiovascular disease in black adults from the tri-county area of metropolitan Jackson, Mississippi. Participants completed baseline questionnaires between 2000 and 2004 on modifiable lifestyle risk factors, including physical activity, time spent watching television, dietary intake via a 158-item food frequency questionnaire, smoking status, alcohol use and sleep-disordered breathing burden. Researchers created a modifiable lifestyle risk factor score, stratifying participants by three categories: poor (0–3 points); average (4–7 points); and optimal (8–11 points). Researchers also measured fasting glucose and insulin, HbA1c, total adiponectin and estimated insulin resistance using homeostatic model assessment for insulin resistance. Incidence rate ratios (IRR) for diabetes were estimated using Poisson regression models adjusted for age, sex, education, occupation, systolic blood pressure and BMI.
After a median follow-up of 7.6 years, 560 participants developed type 2 diabetes, for an incidence rate of 22.9 per 1,000 person-years (mean age, 53 years; 64% women). The incident diabetes rates per 1,000 person-years among participants in poor, average or optimal modifiable risk categories were 28.7, 22.9 and 16.9, respectively.

After adjusting for covariates including BMI, researchers found that the association between individual risk factors and incident diabetes trended in the expected direction, but was not significant. However, for the combined modifiable risk factor score, those in the average score group were 21% less likely to develop diabetes vs. those in the poor score group; those in the optimal score group were 31% less likely to develop diabetes vs. those with poor lifestyle scores.

“A modifiable risk factor category increase (poor to average or average to optimal) was associated with an 18% lower risk of incident diabetes (P = .03),” the researchers wrote. “Similar results were seen with adjustment for waist circumference instead of BMI.”

Researchers also found that baseline obesity status played a role in the effect of lifestyle changes on diabetes risk. Among participants with a BMI of 30 kg/m² or less, those with average or optimal risk scores saw a 40% and 47% reduced risk for diabetes, respectively, compared with those in the poor lifestyle score group. Among those in the average or optimal score groups with a BMI of at least 30 kg/m², IRR was markedly higher at 0.9 (95% CI, 0.67-1.21) and 0.83 (95% CI, 0.51-1.34), respectively.

“A key finding is that the associations varied by BMI, waist circumference and baseline glycemic status, with the greater magnitude of associations observed among participants with BMI < 30, normal waist circumference and normoglycemia at baseline,” the researchers wrote. “A combination of clinical practice guidelines that emphasize a healthy lifestyle in metabolically normal [African-Americans] and public health policies that focus on primordial prevention by directing resources to increase physical activity and healthy diet while reducing sedentary activities and smoking are likely necessary to reduce the burden of diabetes in [African-American] communities.” – by Regina Schaffer

Disclosures: The authors report no relevant financial disclosures.