1. From this cohort study, low aerobic capacity and low muscular strength in youth were independently associated with an increased risk of developing type 2 diabetes mellitus later in adulthood.
Evidence Rating Level: 2 (Good)
Study Rundown: It is well established that sedentary lifestyle is a risk factor for type 2 diabetes mellitus (T2DM). However, few studies have used objective metrics to determine the long-term impacts of physical fitness on the development of T2DM. In this study, the aerobic capacity and muscular strength of 18-year-old males was correlated with individual future medical records. The development of T2DM later in life was associated with low socioeconomic status, less education, family history of T2DM and higher mean BMI. Those individuals with both low aerobic capacity and low muscular strength had the highest risk of T2DM development, even in men with normal BMI, but these two measures of physical fitness did not act synergistically. This study was limited in that it only included males, which may decrease its generalizability. The national sample size, prospectively measured data and high inclusivity of the cohort were its major strengths. These results demonstrate that low aerobic capacity and/or low muscular strength in adolescence may be important factors contributing to the risk of developing T2DM in adulthood.
In-Depth [prospective cohort]: Using the Swedish Military Conscription Registry, data from 1969-1997 on 1,534,425 male 18-year-old military conscripts comprised the study cohort. Muscle strength (MS) and aerobic capacity (AC) were measured quantitatively using continuous variables and individuals were organized into tertiles for each variable. Conscripts were followed for a mean 25.7 years (max follow-up of 62 years). At a median age of 46.8 years, 34,008 (2.2%) developed type 2 diabetes mellitus (T2DM). Regardless of MS, low AC after 10, 20, 30 or 40 years of follow-up was associated with increased cumulative incidence of T2DM, whereas low MS only had this effect after 40 years. Those with both low MS and low AC had the highest incidence (4.45% at 40y) and highest risk of developing T2DM (HR 3.07; p <0.001). Low aerobic capacity and low muscular strength were independently associated with the risk of developing T2DM with an additive, not multiplicative, positive interaction.
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