How sleep duration impacts cognitive status among Indian population aged ≥45 years: Evidence from Longitudinal Aging Study India (LASI)

Introduction: An aging population is associated with an increased risk of cognitive decline. Sleep duration, both excess and deficiency, is a risk factor for cognitive impairment. Therefore, this study was conducted to assess the relationship between sleep duration and cognition in the Indian population. Methods: This study was a secondary analysis of the first wave of the Longitudinal Aging Study in India (LASI) conducted across India in all 34 states and union territories. Sleep duration was calculated using sleep and wake times, whereas cognition was measured as a composite cognitive index. Both univariable and multivariable linear regressions were performed on the composite cognitive score. Subgroup analyses were conducted based on sex and age groups (45-59 years and ≥60 years). Results: The median (IQR) cognition score was 25 (20-30). A sleep duration of ≤4 hours was associated with a decrease in cognition status of 1.15 points (1.57-0.72), and a sleep duration of ≥9 hours was associated with a decrease of 0.93 points (1.25-0.60). Subgroup analysis revealed that this relationship remained consistent across both genders and both age groups. Conclusion: Both long and short durations of sleep were seen to be associated with a decrease in cognition scores among Indian adults, in both sexes and both age groups. Thus, proper sleep duration can help in the prevention of declining cognition as one ages and the development of dementia.