American Journal of Medicine, internal medicine, medicine, health, healthy lifestyles, cancer, heart disease, drugs

Serum Insulin and Cognitive Performance in Older Adults: A Longitudinal Study

The aim of this study was to examine the association of serum glucose, insulin, and insulin resistance with cognitive functioning 7 years later in a longitudinal population-based study of Finnish older adults.

Methods

Serum glucose and insulin were measured at baseline in 269 dementia-free individuals aged 65-79 years, from the Cardiovascular Risk Factors, Aging, and Dementia (CAIDE) study. Insulin resistance was estimated with the homeostasis model assessment (HOMA-IR). Participants were reexamined 7 years later, and global cognition, episodic memory, executive functioning, verbal expression, and psychomotor speed were assessed, both at baseline and at follow-up. Multiple linear regression was used to investigate the associations with cognitive performance at follow-up, after adjusting for several potential confounders, including common vascular risk factors.

Results

In the multivariable-adjusted linear regression models, no associations of insulin resistance with cognitive functioning were observed. After excluding 19 incident dementia cases, higher baseline HOMA-IR values were related to worse performance in global cognition (β [standard error (SE)] -.050 [0.02]; P = .043) and psychomotor speed (β [SE] -.064 [.03]; P = [.043]) 7 years later. Raised serum insulin levels were associated with lower scores on global cognition (β [SE] -.054 [.03]; P = .045) and tended to relate to poorer performance in psychomotor speed (β [SE] -.061 [.03]; P = .070).

Conclusions

Serum insulin and insulin resistance may be independent predictors of cognitive performance 7 years later in elderly individuals without dementia. Randomized controlled trials are needed to determine this issue.

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-Babak Hooshmand, MD, PhD, MPHa,b, Minna Rusanen, MD, PhDc,d, Tiia Ngandu, MD, PhDd, Jaana Leiviskä, PhDe, Shireen Sindi, PhDa, Christine A.F. von Arnim, MDb, Peter Falkai, MDf, Hilkka Soininen, MD, PhD,c,g, Jaakko Tuomilehto, MD, MA, PhD, FRCPe,h,i,j,k,l, Miia Kivipelto, MD, PhDa,c,m

-This article originally appeared in the March issue of The American Journal of Medicine.

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