Introduction: Left ventricular hypertrophy assessed by electrocardiography (ECG-LVH) is a marker of subclinical cardiac damage and a strong predictor of cardiovascular events. The prevalence of ECG-LVH is increased in obesity and type 2 diabetes; thus, exercise and weight loss are recommended to lower cardiovascular disease (CVD) risk in these individuals. However, there are no data on the long term effects of diet- and/or exercise-induced weight loss on ECG-LVH.
Hypothesis: We hypothesized that an intensive lifestyle intervention targeting weight loss through caloric restriction and increased physical activity reduces the incidence of ECG-LVH in overweight and obese adults with type 2 diabetes.
Methods: We included 4,549 Look AHEAD participants without ECG-LVH at baseline who were randomized to a 10-year lifestyle intervention (ILI, n=2,287) or diabetes support and education (DSE, n=2,262) (mean age = 58.7±6.8 years, 64.5% White). ECG-LVH defined by the Cornell voltage criteria (RaVL + SV3 >2800 μV in men and >2000 μV in women) was assessed every 2 years. Proportional hazards regression was used to compare the incidence of ECG-LVH (defined as time to first occurrence) and mixed models were used to compare changes in absolute Cornell voltage over time between intervention groups, with tests of interactions by gender, race/ethnicity and baseline CVD status. Analyses were performed according to the intention-to-treat principle and all available follow-up data were included.
Results: Baseline characteristics were similar between intervention groups, except for lower systolic blood pressure in the ILI vs. DSE group: mean (SE) = 127.6 (0.4) mmHg vs. 129.0 (0.4) mmHg, respectively (p=0.007). Over a median 9.5 years of follow-up, there were 162 cases of incident ECG-LVH in the ILI group (7.1%) and 181 cases in the DSE group (8.0%): HR=0.89, 95% CI=0.71-1.09, p=0.24. Intervention group interactions were not significant for prior CVD (p=0.53) or gender (p=0.74), but were of borderline significance for race/ethnicity (p=0.058). Among African Americans, ILI was estimated to be protective relative to DSE (HR=0.59, 95% CI= 0.38-0.91); there was no significant interaction for other race/ethnicity groups. Similar results were found after multivariate adjustment. In the mixed model analysis, the mean (SE) Cornell voltage was slightly lower in the ILI group compared to the DSE group after adjusting for the baseline value, age, gender, race/ethnicity, and prior CVD: 1369.2 (5.4) μV vs. 1381.9 (5.4) μV, respectively (p=0.07). Accounting for changes in blood pressure and anti-hypertensive medication use did not alter the results.
Conclusions: A long-term intensive lifestyle intervention in overweight and obese adults with type 2 diabetes does not significantly lower overall incident ECG-LVH. The protective effect observed in African Americans, however, warrants further investigation.