Nonlinear associations of depression and sleep duration with cognitive impairment in older adults with hypertension: Findings from a national survey

Huiying Fan^1,2,3*He-Li Sun^1,3Feng Yuan⁴Qinge Zhang⁴Hua-Qing Xing^1,3Qian-Hua Huang^1,3Zhaohui Su⁵Teris Cheung⁶Chee H Ng⁷Yu-Tao Xiang^1,3Gang Wang⁴

• ¹Unit of Psychiatry, Department of Public Health and Medicinal Administration, & Institute of Translational Medicine, Faculty of Health Sciences, University of Macau, Macau, China
• ²International Nursing School, Hainan Medical University, Haikou, Hainan Province, China
• ³Centre for Cognitive and Brain Sciences, University of Macau, Macau, Shanghai Municipality, China
• ⁴National Clinical Research Center for Mental Disorders, Beijing Anding Hospital, Capital Medical University, Beijing, China
• ⁵School of Public Health, Southeast University, Nanjing, Jiangsu Province, China
• ⁶School of Nursing, Faculty of Health and Social Sciences, Hong Kong Polytechnic University, Kowloon, Hong Kong, SAR China
• ⁷Department of Psychiatry, The Melbourne Clinic and St Vincent's Hospital, University of Melbourne, Richmond, Australia

Objectives: Cognitive impairment is a major health concern in older adults with hypertension, and both depression and abnormal sleep duration are recognized as potential contributing factors. This study aimed to explore the non-linear association of depression and sleep duration with cognitive impairment among older adults with hypertension. Methods: This cross-sectional study was based on the 2017-2018 wave of Chinese Longitudinal Healthy Longevity Survey. Depression and cognitive function were measured using the 10-item Center for Epidemiological Studies Short Depression Scale and Mini Mental State Examination, respectively. Univariate, binary logistic regression, and restricted cubic spline regression analyses were used to examine the associations between depression, sleep duration and cognitive impairment.Results: A total of 3,989 older adults with hypertension were included. The prevalence of depression and cognitive impairment were 28.1% (95%CI=26.7-29.5%) and 10.1% (95%CI= 9.2-11.1%), respectively. After adjusting for confounding factors, a significant linear association (nonlinear P=0.814) between depression and cognitive impairment risk was found, while a Ushaped nonlinear association was identified between sleep duration and cognitive impairment risk (P=0.040). Both shorter (<6.6 hours) and longer (>7.7 hours) sleep duration per day were associated with higher cognitive impairment risk, with an inflection point at 7.3 hours. The effect of sleep duration on cognitive impairment risk was more significant for participants with a higher (≥ 6 years) education level.This study highlights the importance of managing depression and optimizing sleep duration in addressing the risk of cognitive decline in older adults with hypertension.