Sleep quality and quantity often decrease as people age, but whether this is associated with risk of cognitive decline is a subject of ongoing investigation.
To better understand the potential relationship between sleep and cognitive decline, Dr Claudine Berr of INSERM, Montpellier, France, and colleagues examined data from the French Three-City Study, an ongoing, long-term, multisite study of the relationship between vascular disease and dementia in community-dwelling individuals age 65 or older. Cognitive data were obtained at baseline and at 2, 4, and 8 years’ follow-up; an ancillary project gathered data on sleep complaints at baseline.
Researchers analyzed data from 4,894 nondemented study participants who had completed sleep questionnaires, had Mini Mental State Examination (MMSE) scores of greater than or equal to 24 at baseline, and for whom data from at least one follow-up evaluation were available. Cognitive decline was defined as a decrease of four or more points on the MMSE at the three follow-up points. Researchers analyzed data for each of the five subcomponents of insomnia: (1) poor sleep quality, (2) difficulty initiating sleep, (3) difficulty maintaining sleep, and (4) early morning awakening; and (5) excessive daytime sleepiness.
They found that excessive daytime sleepiness, which was reported by 17.9% of participants, independently increased risk of cognitive decline. In contrast, difficulty maintaining sleep, reported by 63.5% of participants, was negatively associated with risk of cognitive decline.
"These results suggest that excessive daytime sleepiness may be an early predictor of cognitive decline and that sleep complaints should be adequately evaluated in older persons," said the study’s researchers.
The research was reported at the Alzheimer’s Association International Conference 2012 (AAIC 2012) in Vancouver.