PM Association Between Silent Lacunar Infarcts And Muscle Strength: The Bunkyo Health Study

Abstract

Silent lacunar infarcts by definition, lack clinically overt stroke-like symptom, are occasionally found by brain magnetic resonance imaging (MRI) scan in asymptomatic elderly individuals. A previous study revealed that more than 25% of elderly people have silent lacunar infarcts. The main risk factors for lacunar infarcts and stroke were reported as aging, hypertension, and smoking. While a recent study showed that low muscle strength is also a risk factor for cerebrovascular events, it remains unclear whether low muscle strength is a risk factor for silent lacunar infarcts. PURPOSE: To investigate the association between muscle strength and silent lacunar infarcts in the elderly people living in urban community. METHODS: This study included 1,536 elderly people without past history of cerebral vascular events, aged 65-84 years living in an urban area of Tokyo, Japan (Bunkyo Health Study). All participants underwent brain MRI scan and silent lacunar infarcts were defined as the presence of 1 or more lacunar infarcts. Isokinetic muscle strength of knee extensors was evaluated at angular velocity of 60 degree per seconds using dynamometer. Subjects was categorized tertiles (high, medium, and low) by muscle strength, and compared the prevalence of silent lacunar infarcts. RESULTS: Mean age of subjects was 73.0±5.4 years old and 58.9% were female. Two hundred fifty-two (16.4%) subjects were diagnosed as silent lacunar infarcts, and the subjects categorized as lower muscle strength showed higher prevalence of silent lacunar infarcts (high: 12.3%, medium: 17.7%, and low: 19.3%, p for trend 0.003), while skeletal muscle indices among the groups were similar. After multivariate adjustment by age, sex, body mass index, smoking status, physical activity, hypertension, diabetes, and dyslipidemia, the trend was still significant and the odds ratio for having silent lacunar infarcts was significantly higher in the lowest muscle strength tertile compared to the highest tertile [(High: 1.00 (reference), medium: 1.42 (95%CI: 0.98-2.04), Low: 1.48 (1.02-2.14), p for trend 0.043]. CONCLUSIONS: In the elderly people living in urban community, lower muscle strength of knee extensors was associated with higher prevalence of silent lacunar infarcts independent of other established risk factors.