Racial Differences in the Association of Insulin Resistance With Stroke Risk

Abstract

Background and Purpose Insulin resistance is associated with increased stroke risk, but the effect has not been adequately examined separately in white and black populations. Methods The association of baseline insulin resistance with risk of cerebral infarction (CI) and intracerebral hemorrhage (ICH) was assessed in 12,366 white and 6,782 black participants from the REGARDS cohort, recruited between 2003 and 2007 and followed an average of 5.7 years. Insulin resistance was measured with the homeostasis model assessment (HOMA-IR). Results There were 364 incident CI and 41 incident ICH events. The risk for CI increased with the log of insulin resistance in whites (HRln(IR) = 1.17; 95% CI: 1.00 – 1.38), but was largely attenuated by adjustment for stroke risk factors (HRln(IR) = 1.05; 95% CI: 0.88 – 1.26). There was no association in blacks (HRln(IR) = 1.01; 95% CI: 0.81 – 1.25). After adjustment for demographic factors and risk factors, there was a significant difference by race in the association of insulin resistance with risk of ICH (p = 0.07), with a decrease in the risk of ICH in whites (HRln(IR) = 0.61; 95% CI: 0.35 – 1.04) but a non-significant increase for blacks (HRln(IR) = 1.20; 95% CI: 0.60 – 2.39). Conclusion These data support the growing evidence that insulin resistance may play a more important role in stroke risk among white than black individuals, and suggest a potentially discordant relationship of insulin resistance on CI and ICH among whites.

Sex Differences in the Association Between Insulin Resistance and Incident Coronary Heart Disease and Stroke Among Blacks Without Diabetes Mellitus: The Jackson Heart Study

“…Our findings of a positive association between IR (as measured by HOMA‐IR) and CHD or an inverse association between insulin sensitivity (as measured by the McAuley index) and CHD are consistent with previous studies in predominantly white populations 6, 7, 8, 9. Prior studies that investigated sex differences in the association between IR and CVD found varying effects depending on which measure was used; the association was stronger in men than in women using HOMA‐IR, but the opposite was found using fasting insulin and fasting glucose 6…”

“…A number of studies have reported no association between IR and stroke in blacks, primarily using HOMA‐IR and fasting insulin 7, 8. Howard et al, using data from the REGARDS study, reported a significant association between HOMA‐IR and ischemic stroke risk in whites, but not in blacks, though no significant race interaction was found 8.…”

“…Howard et al, using data from the REGARDS study, reported a significant association between HOMA‐IR and ischemic stroke risk in whites, but not in blacks, though no significant race interaction was found 8. However, the relationship between HOMA‐IR and intracerebral hemorrhage was different; there was a trend towards a decrease in risk of intracerebral hemorrhage in whites (HR 0.61, 95% CI: 0.35–1.04) and an increase in risk in blacks (HR 1.20, 95% CI: 0.60–2.39).…”

“…For logHOMA‐IR, interaction tests for the composite outcome and CHD models were significant, and thus our analyses are stratified by sex. The association between IR and ischemic stroke appears to differ from that with intracerebral hemorrhage,8 so we performed a sensitivity analysis including only cases of ischemic stroke. All analyses were performed using SAS 9.3 (SAS Institute Inc, Cary, NC).…”

“…In the Atherosclerosis Risk in Communities (ARIC) study, fasting insulin was associated with incident stroke in whites but not in blacks ( P interaction =0.036) 7. In the Reasons for Geographic And Racial Differences in Stroke (REGARDS) study, HOMA‐IR was associated with stroke risk in whites, but not in blacks 8. However, the authors did not find a significant race interaction.…”