Fasting insulin and risk of cerebral infarction in a Japanese general population: The Jichi Medical School Cohort Study

Objective: We investigated the relation between fasting insulin (FI) and risk of cerebral infarction in a Japanese general population. Methods: The subjects were 2,610 men and women without past history of stroke or myocardial infarction and under treatment for diabetes, examined between 1992 and 1995 as part of the Jichi Medical School Cohort Study. The FI level was measured once at the baseline. Subjects were divided into quintiles by FI levels, and Cox’s proportional hazard model was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for cerebral infarction. Results: During an average of 11.1 years of follow-up, 87 participants developed cerebral infarction. Crude incidence rates of FI quintiles 1-5 were 4.69, 2.35, 1.85, 2.77 and 3.30 per 1,000 person-years, respectively. The multivariate-adjusted HRs for cerebral infarction were 2.33 (95% CI, 1.10 – 4.96) in quintile 1 (Q1), 1.25 (95% CI, 0.55 – 2.84) in Q2, 1.68 (95% CI, 0.76 – 3.70) in Q4 and 2.06 (95% CI, 0.94 – 4.47) in Q5, using Q3 as the reference. Conclusions: The lowest FI level was associated with increased risk of cerebral infarction and the association between FI and risk of cerebral infarction appeared to be a U-shaped relationship. Neurology Asia 2013; 18(4) : 343 – 348 Address correspondence to: Yuji Kaneda, Department of Surgery, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan. Tel: +81-285-58-7371, Fax: +81-285-44-3234, E-mail: [email protected] INTRODUCTION Insulin resistance is defined as a state of subnormal biologic response to a given concentration of insulin, and it is well established that insulin resistance is independently associated with risk of stroke. To assess insulin resistance, several indices have been used, such as the homeostasis model assessment, but it is rare to use fasting insulin (FI) solely. The relation between FI and stroke was investigated in several prospective studies, but this relation is controversial. In addition, little is known about the relationship between FI and the risk of cerebral infarction in a Japanese general population. The purpose of this study was to examine the relationship between insulin resistance measured by FI and cerebral infarction in a Japanese general population in a prospective study. METHODS