Associations between sleep duration and cognitive impairment in mild cognitive impairment

Abstract

Summary The prevalence of mild cognitive impairment (MCI) increases among elderly people and is associated with a high risk of dementia. Identifying factors that may contribute to the progress of MCI to dementia is critical. The objective of this study was to examine the association of objective sleep with cognitive performance in MCI patients. A subsample of 271 participants with a diagnosis of probable Alzheimer's disease (AD; N = 50) or mild cognitive impairment (MCI; N = 121) and 100 persons who were not cognitively impaired (NI) were recruited from a large population‐based cohort in the island of Crete, Greece (3140 older adults aged >60 years). All participants underwent extensive neuropsychiatric/neuropsychological evaluation and a 3‐day 24‐hr actigraphy. Objective sleep variables and their association with neuropsychological performance were examined across the three groups, controlling for demographics, body mass index, depression, sleep apnea symptoms and psychotropic medications. Patients with AD had significantly longer 24‐hr total sleep time (TST) compared to the MCI and NI groups. Long 24‐hr TST was associated with reduced performance on tasks that placed significant demands on attention and processing speed in the MCI group and the AD group. Elderly patients with MCI have similar objective sleep duration to normal controls, whereas AD patients sleep longer. Long sleep duration in patients with multidomain subtypes of MCI is associated with critical non‐memory cognitive domains. It appears that within the MCI group those that sleep longer have more severe cognitive impairment.

Poor Diet, Long Sleep, and Lack of Physical Activity Are Associated with Inflammation among Non-Demented Community-Dwelling Elderly

“…A study based on objective actigraphic sleep found a U-shape association between sleep duration and all-cause mortality among elderly [ 66 ]. Several studies have reported associations between long sleep duration and cardiovascular disease, coronary heart disease, cognitive decline, and all-cause mortality in this age group [ 43 , 67 , 68 , 69 , 70 ]. It appears that objective long sleep is a result/marker of increased inflammation in elderly subjects [ 65 ].…”

“…We propose that adopting a diet rich in vegetables and a physically active lifestyle, by lowering inflammation, could help reduce mortality and morbidity, including cognitive decline among elderly. Furthermore, given that long sleep seems to relate with inflammation levels, as well as cognition and disease severity among elders with cognitive decline [ 42 , 43 , 86 ], we and others have previously reported that treatment with sedative/sleep-prolonging psychotropic medication in this population should be given with caution [ 42 , 43 , 86 , 87 ]. These simple practical recommendations could be easily applied in a primary care setting.…”

“…Based on that, we divided the sample to the top 25% of persons above the median percent sleep time (long sleep duration group), and the 75% of persons in the bottom half (normal sleep duration group). We then rounded the cut-off points to meaningful numbers and thus created the following two sleep duration groups: the long sleep duration group consisted of those who slept ≥7.5 h (coded as 1), and the normal sleep duration group of those who slept <7.5 h (coded as 0) [ 43 ].…”

Subjective sleep parameters in prodromal Alzheimer’s disease: a case-control study

“…Differently from our results, some of them have associated longer sleep times with reduced cognitive performance. 3,20 The use of a subjective sleep assessment could explain the lower sleep duration shown by our MCI-MD participants. One study found that people with MCI reported shorter sleep times and worse sleep quality when compared with data obtained by objective methods.…”

“…Differently from our results, some of them have associated longer sleep times with reduced cognitive performance. 3 , 20 …”