Short sleep duration in midlife may increase risk of dementia in later life

Midlife adults aged between 50 and 70 years who reported a short sleep duration of ≤6 hours/night had an increased risk of developing dementia later in life, according to a study presented at AAIC 2021.

Using data from the Whitehall II cohort study, the researchers analysed 7,959 adults aged 50, 60, and 70 years who were categorized according to their self-reported sleeping duration, categorized as short (≤6 hours), normal (7 hours), and long (≥8 hours) sleeping hours a night. At a mean follow-up of 24.6 years, 521 participants (42.0 percent female) were diagnosed with dementia obtained from electronic health records of the UK National Health Services. [AAIC 2021, abstract 55133]

Subjects aged 50 and 60 years with short sleep duration demonstrated an increased risk of incident dementia at a mean follow-up of 25 and 15 years (hazard ratio [HR], 1.22, 95 percent confidence interval [CI], 1.01–1.48 and HR, 1.37, 95 percent CI, 1.10–1.72, respectively).

Although not significant, an increased risk of incident dementia was also observed among those aged 70 years who reported short sleep duration at a mean follow-up of 8 years (HR, 1.24, 95 percent CI, 0.92–1.57).

When trajectories of sleep duration between patients aged 50 and 70 years and risk of dementia were assessed, persistent short sleep duration was associated with a 30 percent increased risk of dementia (HR, 1.30, 95 percent CI, 1.00–1.69).

The researchers also found that among subjects without a history of mental disorders before 65 years of age, an increased risk of dementia was evident in the short sleep duration group compared with the long sleep duration group (HR, 1.25 vs 1.23 for aged 50 years and HR, 1.28 vs 1.20 and 1.22 for both aged 60 and 70 years, respectively).

An additional analysis was performed based on accelerometer-assessed sleep duration in a subsample, similar results were observed and showed that short sleep duration was also associated with an increased risk of dementia, said lead author Dr Séverine Sabia from the University College London, London, UK.

“[Overall,] measurement of sleep duration at age 50, 60, and 70 years along with [the] change in sleep duration over this period provides consistent results for increased risk of dementia in those with short sleep [duration],” the researchers noted. [Nat Commun 2021;doi:10.1038/s41467-021-22354-2]

“[These findings suggest] that short sleep duration in midlife is associated with an increased risk of dementia … [and also] could be a potential risk factor for [late-onset] dementia, … [and therefore,] sleep duration is likely to be important for brain health,” Sabia concluded.

“Further research is required to understand the mechanisms underlying the association between sleep and dementia over the course of dementia pathogenesis,” they added.