Sleep difficulties, incident dementia and all-cause mortality among older adults across 8 years: Findings from the National Health and Aging Trends Study

Abstract

Sleep difficulties have been implicated in the development and progression of dementia and in all-cause mortality. This study examines the relationship between sleep difficulties, incident dementia and all-cause mortality over 8 years of follow-up among a nationally representative sample of older (≥65 years) adults in the United States. We used data collected from the National Health and Aging Trends Study (NHATS) from 2011 to 2018, a prospective cohort study of Medicare beneficiaries. At baseline, the NHATS sample comprised 6,376 older adults who were representative of 32 million older adults. Respondents reported routine difficulty initiating sleep or difficulty falling back asleep "most nights" or "every night" in each study year. In each year, dementia was determined by either self-reported diagnosis or performance on immediate and delayed recall word and clock drawing tests, whereas all-cause mortality was determined by proxy. We conducted Cox proportional hazards modelling, adjusting for age, sex, marital status and chronic conditions. In models predicting all-cause mortality, we also controlled for dementia. Among respondents at baseline, 19% were 65-75 years of age, 71% identified as non-Hispanic white and 59% were female. Difficulty initiating sleep (hazard ratio [HR], 1.49; 95% confidence interval [CI],1.25-1.77), difficulty falling back asleep (HR, = 1.39; 95% CI,1.14-1.70) and concurrent sleep difficulties (HR, 1.58; 95% CI, 1.25-1.99) were associated with greater risk of dementia. Difficulty initiating sleep (HR, 1.44; 95% CI,1.20-1.72), difficulty falling back asleep (HR, 1.56; 95% CI,1.29-1.89), and concurrent sleep difficulties (HR, 1.80; 95% CI, 1.44-2.24) were associated with greater risk of all-cause mortality. Our findings demonstrate that reported difficulties are prospectively associated with an increased risk of dementia and all-cause mortality among older people.

Keywords: geriatric medicine; gerontology; insomnia; sleep difficulties; sleep medicine.

Figure 1a. Estimated survival curves from adjusted cox models for incident dementia in the sleep difficulty or comparison conditions, controlling for covariates.

Estimated survival curve from adjusted cox model for incident dementia in the difficulty initiating sleep and comparison conditions, controlling for covariates. ^a The red line represents the respondents who reported each sleep difficulty “most nights” or “every night.” In the case of concurrent difficulties, the red line represents the respondents who reported both sleep difficulties “most nights” or “every night.” ^b The blue line represents respondents who did not report difficulty (i.e., reported “never,” “rarely,” or “some nights”). In the case of concurrent difficulties, the blue line represents the respondents who reported both sleep difficulties “never,” “rarely,” or “some nights.” ^c Respondents who screened positive for dementia at baseline were removed. ^d The curves represent covariate-adjusted analyses (i.e., age, sex, education, marital status, and chronic conditions).

Figure 1b. Estimated survival curves from adjusted cox models for incident dementia in the sleep difficulty or comparison conditions, controlling for covariates.

Estimated survival curve from adjusted cox model for incident dementia in the nighttime awakening and comparison conditions, controlling for covariates. ^a The red line represents the respondents who reported each sleep difficulty “most nights” or “every night.” In the case of concurrent difficulties, the red line represents the respondents who reported both sleep difficulties “most nights” or “every night.” ^b The blue line represents respondents who did not report difficulty (i.e., reported “never,” “rarely,” or “some nights”). In the case of concurrent difficulties, the blue line represents the respondents who reported both sleep difficulties “never,” “rarely,” or “some nights.” ^c Respondents who screened positive for dementia at baseline were removed. ^d The curves represent covariate-adjusted analyses (i.e., age, sex, education, marital status, and chronic conditions).

Figure 1c. Estimated survival curves from adjusted cox models for incident dementia in the sleep difficulty or comparison conditions, controlling for covariates.

Estimated survival curve from adjusted cox model for incident dementia in the concurrent sleep difficulty and comparison conditions, controlling for covariates. ^a The red line represents the respondents who reported each sleep difficulty “most nights” or “every night.” In the case of concurrent difficulties, the red line represents the respondents who reported both sleep difficulties “most nights” or “every night.” ^b The blue line represents respondents who did not report difficulty (i.e., reported “never,” “rarely,” or “some nights”). In the case of concurrent difficulties, the blue line represents the respondents who reported both sleep difficulties “never,” “rarely,” or “some nights.” ^c Respondents who screened positive for dementia at baseline were removed. ^d The curves represent covariate-adjusted analyses (i.e., age, sex, education, marital status, and chronic conditions).

Figure 2a. Estimated survival curves from adjusted cox models for all-cause mortality in the sleep difficulty or comparison conditions, controlling for covariates.

Estimated survival curve from adjusted cox model for all-cause mortality in the difficulty initiating sleep and comparison conditions, controlling for covariates. ^a The red line represents the respondents who reported each sleep difficulty “most nights” or “every night.” In the case of concurrent difficulties, the red line represents the respondents who reported both sleep difficulties “most nights” or “every night.” ^b The blue line represents respondents who did not report difficulty initiating sleep (i.e., reported “never,” “rarely,” or “some nights”). In the case of concurrent difficulties, the blue line represents the respondents who reported both sleep difficulties “never,” “rarely,” or “some nights.” ^c Respondents who screened positive for dementia at baseline were removed. ^d The curves represent covariate-adjusted analyses (i.e., age, sex, marital status, education, chronic conditions, and dementia).

Figure 2b. Estimated survival curves from adjusted cox models for all-cause mortality in the sleep difficulty or comparison conditions, controlling for covariates.

Estimated survival curve from adjusted cox model for all-cause mortality in the nighttime awakening and comparison conditions, controlling for covariates. ^a The red line represents the respondents who reported each sleep difficulty “most nights” or “every night.” In the case of concurrent difficulties, the red line represents the respondents who reported both sleep difficulties “most nights” or “every night.” ^b The blue line represents respondents who did not report difficulty initiating sleep (i.e., reported “never,” “rarely,” or “some nights”). In the case of concurrent difficulties, the blue line represents the respondents who reported both sleep difficulties “never,” “rarely,” or “some nights.” ^c Respondents who screened positive for dementia at baseline were removed. ^d The curves represent covariate-adjusted analyses (i.e., age, sex, marital status, education, chronic conditions, and dementia).

Figure 2c. Estimated survival curves from adjusted cox models for all-cause mortality in the sleep difficulty or comparison conditions, controlling for covariates.

Estimated survival curve from adjusted cox model for all-cause mortality in the concurrent sleep difficulty and comparison conditions, controlling for covariates. ^a The red line represents the respondents who reported each sleep difficulty “most nights” or “every night.” In the case of concurrent difficulties, the red line represents the respondents who reported both sleep difficulties “most nights” or “every night.” ^b The blue line represents respondents who did not report difficulty initiating sleep (i.e., reported “never,” “rarely,” or “some nights”). In the case of concurrent difficulties, the blue line represents the respondents who reported both sleep difficulties “never,” “rarely,” or “some nights.” ^c Respondents who screened positive for dementia at baseline were removed. ^d The curves represent covariate-adjusted analyses (i.e., age, sex, marital status, education, chronic conditions, and dementia).