NOMAS: insulineresistentie risicofaktor voor stroke
NOMAS supports insulin resistance as stroke risk factor
Analysis of the Northern Manhattan Study (NOMAS) shows that insulin resistance is strongly predictive of ischemic stroke in people who do not have diabetes.
Stroke risk almost tripled among insulin resistant NOMAS participants relative to those who were insulin sensitive, the researchers report in the Archives of Neurology.
"The implications of these findings are exciting if insulin resistance can be proven to be a causal risk factor for stroke (rather than a marker of increased risk) because insulin resistance cannot only be measured, but also treated," said editorialists Graeme Hankey (Royal Perth Hospital, Australia) and Tan Ze Feng (First Affiliated Hospital of Jinan University, Guangzhou, China).
The analysis included 1509 nondiabetic NOMAS participants, aged 68 years on average. During an average 8.5 years of follow-up, 180 participants suffered a vascular event, including 46 ischemic strokes - an incidence of 3.5 per 1000 person-years.
At study enrollment, the participants' average homeostasis model assessment of insulin resistance (HOMA-IR) index was 2.3. About a quarter of the participants fell within the top quartile (2.8 or higher) and were regarded as being insulin resistant.
These people were at higher vascular risk than those in quartiles 1-3, having higher blood pressure and levels of fasting glucose and triglycerides, and lower levels of high-density lipoprotein cholesterol. They also had a higher average body mass index and were less likely to engage in moderate-to-heavy physical activity.
Ischemic stroke risk was not associated with HOMA-IR as a continuous variable, even after accounting for the above variables. Instead, the team found a clear threshold effect, with participants in the top quartile having a 2.47-fold age-adjusted increase in ischemic stroke risk relative to those in quartiles 1-3. The association was strengthened by accounting for sociodemographics, the metabolic syndrome, and vascular risk factors, with the risk increase rising to 2.83 fold.
Insulin resistance did not predict myocardial infarction or vascular death, note Tatjana Rundek (University of Miami, Florida, USA) and co-workers.
In their editorial, Hankey and Feng noted that the ongoing Insulin Resistance Intervention after Stroke (IRIS) trial should show if treating insulin resistance can actually prevent stroke.
In the meantime, they said that it is "premature" to screen for insulin resistance, but noted that "its measurement may have a role in particular cases in which traditional risk stratification schemes suggest that the patient is at intermediate risk of stroke… and in whom an additional finding of insulin resistance may be sufficiently compelling to supplement lifestyle advice with pharmacological interventions to lower stroke risk."