Time-Varying Insomnia Symptoms and Incidence of Cognitive Impairment and Dementia among Older US Adults.

Nicholas V Resciniti,Valerie Yelverton,Jiajia Zhang,Matthew C Lohman,Bezawit E Kase

doi:10.3390/ijerph18010351

Abstract

There is conflicting evidence regarding the association between insomnia and the onset of mild cognitive impairment (MCI) or dementia. This study aimed to evaluate if time-varying insomnia is associated with the development of MCI and dementia. Data from the Health and Retirement Study (n = 13,833) from 2002 to 2014 were used (59.4% female). The Brief Insomnia Questionnaire was used to identify insomnia symptoms which were compiled in an insomnia severity index, ranging from 0 to 4. In analysis, participants’ symptoms could vary from wave-to-wave. Dementia was defined using results from the Health and Retirement Study (HRS) global cognitive assessment tool. Respondents were classified as either having dementia, MCI, or being cognitively healthy. Cox proportional hazards models with time-dependent exposure using the counting process (start-stop time) were used for analysis. For each one-unit increase in the insomnia symptom index, there was a 5-percent greater hazard of MCI (HR = 1.05; 95% CI: 1.04–1.06) and dementia (HR = 1.05; 95% CI: 1.03–1.05), after fully adjusting. Using a nationally representative sample of adults age 51 and older, this study found that time-varying insomnia symptoms are associated with risk of MCI and dementia. This highlights the importance of identifying sleep disturbances and their change over time as potentially important risk factors for MCI and dementia.

Highlights

Dementia is a progressive neurodegenerative disorder affecting individuals’ brain function, memory, and activities of daily living [1]
Using a nationally representative sample of adults age 51 and older, this study found that time-varying insomnia severity was associated with a greater likelihood of developing
In support of our hypothesis, over 12 years of followup, results suggested that for each additional insomnia symptom, there was a 5 percent greater hazard of incident Mild cognitive impairment (MCI) (HR = 1.05; 95% CI: 1.04–1.06) and dementia (HR = 1.05; 95% CI: 1.03–1.06), after adjusting for baseline gender, race, education, BMI, smoking status, drinking status, and chronic disease index

Summary

Introduction

Dementia is a progressive neurodegenerative disorder affecting individuals’ brain function, memory, and activities of daily living [1]. The prevalence of dementia is expected to triple in the 40 years, leading to an estimated 14 million people with dementia by 2060 [2]. Mild cognitive impairment (MCI) is defined as self- or informant-reported functional impairment or impaired test performance on neuropsychological measures that does not reach the severity of dementia [4]. MCI can be a precursor of dementia [5,6], with over 30 percent of individuals diagnosed with MCI progressing to dementia within five years [1]. MCI is estimated to affect 15–20 percent of older adults in the US [1,7,8,9]. Previous research has identified several modifiable and immutable factors contributing to an individual’s risk for dementia and MCI including socio-demographics, comorbidities, family history, and lifestyle factors [1,5,8,10,11,12]

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