Abstract

Background: Disease-modifying treatments for Alzheimer's disease (AD) are currently unavailable and are the focus of an intensive research effort. We found vitamin B3, nicotinamide (NA), to significantly reduce pathology and improve behavior in AD transgenic mice. These results led us to conduct a double-blind, placebo-controlled randomized clinical trial of NA in mild to moderate AD. Methods: Following randomization, subjects received either NA (n = 15, 1500 mg twice daily) or placebo (n = 16) for 24 weeks. A battery of outcome measures were obtained at baseline and 6- week intervals and included the AD Assessment Scale-Cognitive Subscale, Clinician's Interview-Based Impression of Change Plus Caregiver Input, AD Cooperative Study-Activities of Daily Living Scale, and Clinical Dementia Rating Scale. Results: There were no significant effects of NA on the primary or secondary endpoints. A mild effect of low compliance was observed on word recall and command tasks. There were no differences in adverse events experienced by NA- and placebo-treated groups. Conclusions: This study failed to demonstrate that extended-release NA, or vitamin B3, improves cognitive function in subjects with mild to moderate AD over 24 weeks. The lack of efficacy of NA may have been due to several contributing factors including a low sample size, inclusion of subjects with moderate AD, and a relatively short treatment phase. The results also show that high dose NA is relatively safe in elderly subjects with AD. With the current emphasis on the early diagnosis and treatment of AD, a longer duration of treatment with NA in subjects with preclinical AD and/or mild cognitive impairment (MCI) may be warranted.

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