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14-09-2011 | General practice | Article

Intranasal insulin may slow decline in AD

Abstract

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MedWire News: Patients with amnestic mild cognitive impairment (aMCI) or Alzheimer's disease (AD) may benefit from a twice-daily dose of intranasal insulin, show the results of a pilot study.

The researchers report, in the Archives of Neurology, that intranasal insulin treatment may slow both cognitive and functional decline over 4 months of treatment.

"These results provide an impetus for future clinical trials of intranasal insulin therapy and for further mechanistic studies of insulin's role in the pathogenesis of AD," say Suzanne Craft (Veterans Affairs Puget Sound Health Care System, Seattle, Washington, USA) and colleagues.

The team explains that insulin has "a close relationship" with the β-amyloid peptide, which is the main component of the amyloid plaques that accumulate in the brains of patients with AD.

The randomized, double-blind trial included 64 adults with aMCI and 40 with mild or moderate AD. Over 4 months of treatment, those taking insulin 20 IU twice daily showed significantly better delayed story recall than did those taking placebo, whereas patients taking insulin 40 IU twice daily did not improve versus the placebo group.

However, both groups of insulin users had significantly better scores over time for partner/caregiver-rated function on the Dementia Severity Rating Scale (DSRS) relative to the placebo group.

General cognition, measured on the Alzheimer Disease's Assessment Scale-cognitive subscale (ADAS-cog), also tended to decline less in both insulin groups than in the placebo group. The speed of decline in the placebo group was greatest among the youngest patients; thus, these patients gained statistically significant benefits from intranasal insulin treatment.

Insulin treatment had no overall effects on daily function, as measured on the AD Cooperative Study-activities of daily living (ADCS-ADL) scale. However, on further analysis, the team found preserved function in AD patients taking insulin versus placebo, but not in aMCI patients.

"This pattern is not surprising, given that we used the ADCS-ADL version designed to assess daily function in AD, and given that adults with aMCI, by definition, have no or mild functional deficits," say Craft et al.

"We were, however, able to detect the beneficial effects for insulin-treated participants with either AD or aMCI on our primary functional outcome measure, the DSRS, which has detected similar changes in a previous study. The DSRS is a simpler measure than the ADCS-ADL scale, and study partners reported anecdotally that it was easier to complete, which may have contributed to greater reliability and sensitivity."

By Eleanor McDermid

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