Association between insomnia symptoms and cognitive impairment in the Cretan Aging Cohort

Population aging, characteristic of modern Western societies, is associated with various forms of cognitive decline. Insomnia/insomnia-type symptoms have been reported as modifiable risk factors for cognitive decline. The objective of this study was to examine, in a comprehensive way (a) the prevalence and the risk factors associated with insomnia-type symptoms and (b) the association of insomnia-type symptoms with cognitive impairment in a large, homogeneous, community-dwelling population in the island of Crete, Greece.

Our sample consisted of 3066 community-dwelling elders aged 60-100 years participating in the Cretan Aging Cohort. All participants were interviewed with a structured questionnaire assessing demographics, physical and mental health, sleep, lifestyle habits and cognitive function using the Mini Mental State Examination (MMSE). Furthermore, insomnia-type symptom prevalence was estimated in the presence of one or more sleep complaints. Linear and logistic regression analyses examined (a) the association between insomnia-type symptoms and demographics, physical/mental health and lifestyle and (b) the association between cognition and insomnia-type symptoms.

Prevalence of one or more insomnia-type symptoms was 64.6%. Multivariate analyses showed that female gender, widowhood, benzodiazepine use and physical ailments were significantly associated with insomnia-type symptoms. Multivariate models also showed that insomnia-type symptoms were associated with increased odds of cognitive impairment (p < 0.0001).

In a large population of older people in Crete, Greece, insomnia-type symptoms are very prevalent and associated with increased risk for cognitive impairment. Future studies should assess whether treatment of sleep problems improves or delays the deterioration of cognitive function in older adults.