Insulin Resistance and Muscle Weakness Are Synergistic Risk Factors for Silent Lacunar Infarcts: the Bunkyo Health Study: a Cross Sectional Study

Abstract Background: Previous studies showed that insulin resistance and reduced muscle strength are risk factors for silent lacunar infarcts, but it is unclear whether they are still independent risk factors when adjusted for each other. In addition, the effect of their combination on silent lacunar infarcts is completely unknown.Methods: We evaluated silent lacunar infarcts, insulin sensitivity, and knee extensor muscle strength by magnetic resonance imaging, PREDIM (an index for insulin sensitivity), and dynamometer, respectively, in 1531 elderly people aged 65–84 years living in an urban area of Tokyo. Results: Among the study subjects, 251 (16.4%) had silent lacunar infarcts. Impaired insulin sensitivity (High; 1.00 [reference], Medium; 1.53 [95% confidence interval (CI): 0.94-2.48], Low; 1.86 [95%CI: 1.02-3.39], p for trend 0.047) and reduced muscle strength (High; 1.00 [reference], Medium; 1.40 [95%CI: 0.98-2.02], Low; 1.49 [95%CI: 1.04-2.15], p for trend 0.037) were independently associated with increased risk for silent lacunar infarcts in the fully adjusted model. In terms of combined, subjects classified as having the lowest insulin sensitivity and lowest strength were 4.33 times (95%CI: 1.64-11.45) more likely to have a silent lacunar infarct than those classified as having the highest insulin sensitivity and highest strength.Conclusions: Impaired insulin sensitivity and reduced muscle strength were independently associated with higher risk of silent lacunar infarcts in elderly subjects, and their combination synergistically increased this risk.