Impaired insulin sensitivity and reduced muscle strength, acting either independently or synergistically, are risk factors for silent lacunar infarcts, according to a new study of elderly individuals from Japan published in Science Reports.¹

The study evaluated 1531 elderly subjects from the Bunkyo Health Study residing in an urban area of Tokyo. Their ages ranged from 65 years to 84 years (mean age 73 years). Insulin sensitivity was measured with PREDIM and muscle strength by dynamometer with an objective to examine their effects, individually and combined, on silent lacunar infarcts. All the study participants underwent MRI scans to look for lacunar infarcts.

Out of the 1531 study participants, 251 (16.4%) were found to have silent lacunar infarcts on MRI. Analysis of data for insulin sensitivity revealed an inverse association of silent lacunar infarcts with insulin sensitivity. Also, reduced insulin sensitivity was associated with higher age, lower physical activity and lower muscle strength. Prevalence of cognitive impairment, hypertension, diabetes, dyslipidemia, and cardiovascular disease was higher in individuals with reduced insulin sensitivity.

Both impaired insulin sensitivity and reduced muscle strength were independently found to be associated with an increased risk for silent lacunar infarct; insulin sensitivity - high (odds ratio 1), medium (OR 1.67) and low (OR 2.24) and muscle strength - high (OR 1), medium (OR 1.48), low (OR 1.65). This risk increased further when the effects of the two were considered. The chances of having a silent lacunar infarct increased 4.33 times in patients with the lowest insulin sensitivity and lowest muscle strength when compared with those with the highest insulin sensitivity and highest muscle strength.

Low insulin sensitivity and low muscle strength together had a sensitivity of 68.5%, specificity of 63.0%, positive predictive values of 26.7% and negative predictive values of 91.1% for silent lacunar infarcts.

Lacunar infarcts usually occur in the elderly persons with hypertension and diabetes. They are termed silent lacunar infarcts as they are often an incidental finding on MRI scans. This study has demonstrated that reduced insulin sensitivity and reduced muscle strength increase the risk for silent lacunar infarcts. Atherosclerosis due to increased insulin resistance has been proposed as a cause for the silent infarcts. Reduced muscle strength is associated with silent infarct; conversely, the silent lacunar infarcts can also reduce muscle strength.

Silent lacunar infarcts are predictive of stroke. Quitting smoking, exercising regularly and keeping risk factors such as hypertension, diabetes, blood cholesterol, alcohol intake under control will help prevent silent lacunar infarcts and future stroke, dementia and frailty in the elderly. A healthy lifestyle can lower the risk of having a stroke.

Reference

1. Someya Y, et al. Insulin resistance and muscle weakness are synergistic risk factors for silent lacunar infarcts: the Bunkyo Health Study. Sci Rep. 2021 Oct 26;11(1):21093. doi: 10.1038/s41598-021-00377-5