Poor Sleep Quality and Dementia Linked With Mortality Risk
Poor sleep quality is directly related to mortality risk before adjusting for lifestyle or health-related factors, and dementia was noticeably linked to mortality risk in older White males.
Study results published in the journal Aging demonstrate that poor sleep quality is directly related to mortality risk before lifestyle and health-related factors are adjusted, with probable dementia also observed. The authors note that better research is needed to further assess the link between dementia, mortality risk, and individuals who have better sleep quality.1,2
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The authors explained the importance of investigating the pathways and potential interactions between sleep, dementia, and mortality rates. Inadequate sleep duration and poor sleep quality are becoming increasingly linked to cardiometabolic risk factors and cognitive complications. The occurrence of dementia is indicative of a greater risk of future all-cause mortality, and there is also increasing evidence that suggests that short and lengthy sleep durations—in addition to disturbances—are also associated with higher risks of all-cause mortality.1,2
For this study, the authors assessed whether poor sleep quality mediated or moderated the association between dementia and mortality risk in older US adults, and vice versa. Additionally, they determined whether these associations differed by sex and by race. The investigators investigated the bi-directional associations using data from the Health and Retirement Study, which enrolled a total of 6991 patients who were at least 50 years of age (range: 60-104 years; mean age: 78.1 years). Follow-ups occurred from 2006 from 2020, and a total of 4,938 deaths were recorded with the mortality rate being 74 per 1000 person-years. The follow-up for the participants who survived to the end of 2020 was approximately 15 years.1,2
Sleep quality was conducting using 5 items, with 4 being scored on a Likert scale that ranged from 1 to 3, and the remaining item being scored as a binary outcome. Lifestyle metrics taken into account included smoking status and the frequency of moderate or vigorous activity, both of which were categorized as “never,” “1-4 times per month,” or “more than once per week.” Patients’ gender, race, marital status, education, and total wealth were also recorded. Additionally, except for unchangeable elements (eg, sex and race), any other socio-demographic, lifestyle, and health traits that were assessed in 2006 were considered confounding variables.2
The study results demonstrated that impaired cognitive function assessed in middle to late stages of life was associated with a higher likelihood of mortality, but the specific relationship is still unclear. Cognitive function was also found to be primarily influenced by intricate interplay between environmental and genetic factors over the course of the individual's life, which can also have an influence on health and lifespan. The authors noted that, unlike prior research, this study presented a link between dementia and mortality. The investigators noted that this finding may be a result of the lack of representation of minority racial or ethnic groups because of inaccessible health services to receive a dementia diagnosis.2
Further, sleep quality stratified presented a positive association between dementia and mortality among participants who had better sleep quality. Both mediation and interaction were also involved in explaining the total effects under study, but according to the authors, these statistically significant total effects were mainly made up of controlled directed effects.2
Poor sleep quality was associated with an increased mortality risk, notably in males and White older adults. The association was reversed in the fully adjusted model, with a 7% decrease in risk per tertile. Additionally, probable dementia was correlated with a 2-fold increase in mortality risk with stronger associations present among White adults.2
The authors noted that future research is necessary to further assess these interactions and the groups they affect. “Our findings warrant further exploration of biopsychosocial factors that might influence the sleep and mortality association particularly within men,” said the study authors in a news release.1
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