Regression to the mean contributes to the apparent improvement in glycemia 3.8 years after screening – the ELSA-Brasil Study
Glycemic regression is common in real world settings, but the contribution of regression to the mean (RTM) has been little investigated. We aimed to estimate glycemic regression before and after adjusting for RTM in a free-living cohort of adults with newly ascertained diabetes and intermediate hyperglycemia (IH).
Research Design and Methods
ELSA-Brasil is a cohort study of 15,105 adults screened between 2008-2010 with standardized OGTT and HbA1c, repeated after 3.84 (0.42) years. After excluding those receiving medical treatment for diabetes, we calculated partial or complete regression before and after adjusting baseline values for RTM.
Regarding newly ascertained diabetes, partial or complete regression was seen in 49.4% (95%CI 45.2 – 53.7); after adjustment for RTM, in 20.2% (95%CI 12.1 – 28.3). Regarding IH, regression to normal levels was seen in 39.5% (95%CI 37.9 – 41.3) or in 23.7% (95%CI 22.6% – 24.3%) depending on the WHO or the ADA definition, respectively; after adjustment, corresponding frequencies were 26.1% (95%CI 22.4 – 28.1) and 19.4% (95%CI 18.4 – 20.5). Adjustment for RTM reduced the number of cases detected at screening: 526 to 94 cases of diabetes; 3118 to 1986 cases of WHO-defined IH; and 6182 to 5711 cases of AD-defined IH. Weight loss ≥2.6% was associated with greater regression from diabetes (RR=1.52 95%CI 1.26-1.84) and IH (RR=1.30 95%CI 1.17-1.45).
In this quasi-real-world setting, regression from diabetes at ~4 years was common, less so for IH. Regression was frequently explained by RTM, but, in part, also related to improved weight loss and homeostasis over the follow-up.