Does poor sleep affect cognition differently across ages? Insights from a national cohort

Sleep disturbances are increasingly recognized as important determinants of cognitive functioning, yet evidence from large population-based studies in India remains limited. Understanding how specific sleep problems relate to different cognitive domains across age groups is essential for informing healthy ageing policies.

This study aims to analyse the association between sleep quality such as being unrested, trouble having sleep, night-time/early morning awakening and cognitive performance across domains such as memory, arithmetic ability, orientation, executive functioning, and object naming among Indian adults.

This study analysed data from 62,479 adults aged 18 years and older from the Longitudinal Ageing Study in India (2017-18). Mean cognition scores were compared across categories of sleep disturbances and across three age groups (18-44, 45-59, and ≥60 years). Propensity score matching (PSM) was employed to estimate the effect of various sleep problems on cognitive functioning.

Individuals reporting sleep problems had lower mean cognitive scores. Age differences were prominent, with adults aged ≥60 years consistently showing the lowest scores. Two-way analyses confirmed strong main effects of age and sleep problems. Middle-aged adults (45-59years) with sleep problems showed deficits in orientation and arithmetic performance while among younger adults, sleep problems largely affected memory and orientation. Among young adults, daytime napping increased the memory scores by 0.45 points while feeling unrested despite adequate sleep duration decreased the orientation scores by 0.11 points.

Sleep disturbances are strongly associated with poorer cognitive functioning across multiple domains, with the greatest impact observed among older adults. These findings highlight sleep health as a potentially modifiable determinant of cognitive functioning in a rapidly ageing population.