Short or long sleep duration is associated with memory impairment in older Chinese: the Guangzhou Biobank Cohort Study

Abstract

Study objectives: To examine the association between sleep-related factors and memory impairment.

Design: Cross-sectional study

Setting: Community-based study in Guangzhou, China.

Participants: 28,670 older Chinese (20,776 women and 7,894 men) aged 50 to 85 years.

Measurements and results: Demographic and socioeconomic data, sleep-related factors, and cognitive function were collected by face-to-face interview. Potential confounders, such as employment and occupational status, smoking, alcohol and tea use, physical activity, self-rated health, anthropometry, blood pressure, and fasting plasma glucose and lipids were measured. After adjusting for multiple potential confounders, an inverted U-shaped association between sleep duration and delayed word recall test (DWRT) score, a validated measure of memory impairment, was found, with 7 to 8 h of habitual sleep duration showing the highest score (P-values for trend from 3 to 7 h and from 7 to ≥ 10 h were all ≤ 0.001). Compared to sleep duration of 7 h, the adjusted odds ratio for memory impairment from the sleep duration of 3 to 4 or ≥ 10 h was 1.29 (95% confidence interval 1.07-1.56) and 1.52 (1.25-1.86), respectively. Subjects with daily napping, morning tiredness, or insomnia had significantly lower DWRT scores than those without (P ranged from < 0.001 to 0.01).

Conclusions: Short or long sleep duration was an important sleep-related factor independently associated with memory impairment and may be a useful marker for increased risk of cognitive impairment in older people.

Keywords: Sleep; insomnia; memory impairment; napping; sleep duration.

Figure 1

Adjusted mean MMSE test score (95% confidence interval) by groups of sleep duration (n = 9,237). Adjusting for age, sex, employment, occupation, education, smoking, drinking, physical activity, tea consumption, self-rated health, waist circumference, HDL- and LDL-cholesterol, fasting plasma glucose, systolic blood pressure, napping, morning tiredness, and insomnia factors by memory impairment.