Objective Daytime Napping is Associated with Disease Severity and Inflammation in Patients with Mild to Moderate Dementia1.

BACKGROUND

Patients with dementia report excessive daytime sleep/sleepiness, which is associated with worse cognitive performance. Inflammatory markers may be elevated in patients with dementia and have been proposed as mediators of sleep/sleepiness.

OBJECTIVE

To examine the association of objective daytime napping with cognitive performance and peripheral markers of inflammation in patients with dementia as compared to not cognitively impaired (NCI) controls.

METHODS

A sub-sample of 46 patients with mild-to-moderate dementia and 85 NCI controls, were recruited from a large, population-based cohort of 3,140 elders (≥60 years) in Crete, Greece. All participants underwent medical history/physical examination, extensive neuropsychiatric and neuropsychological evaluation, 3-day 24 h actigraphy and a single morning measure of IL-6 and TNFα plasma levels. Comparisons of sleep parameters and inflammation markers between diagnostic groups, and between nappers and non-nappers within each diagnostic group, were conducted using ANCOVA controlling for demographics/related clinical factors. Associations between inflammatory markers, sleep variables, and neuropsychological performance were assessed within each group using partial correlation analysis controlling for confounders.

RESULTS

Patients with dementia slept 15 minutes longer during the day than NCI. Within dementia patients, nappers had significantly worse performance on autobiographic memory (p = 0.002), working memory (p = 0.007), episodic memory (p = 0.010), and assessment of daily function (p = 0.012) than non-nappers. Finally, IL-6 levels were significantly associated with nap duration within dementia patients who napped (r = 0.500, p = 0.01).

CONCLUSIONS

Daytime napping in patients with dementia is associated with worse cognitive performance and increased IL-6 levels. In dementia, objective daytime napping, may be a marker of the severity of the disease.