Night owls at higher risk of age-related cognitive decline, study finds
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New Delhi: Individuals who identify as night owls — those with a naturally late sleep-wake cycle — may face a higher risk of cognitive decline as they age compared to early risers, according to a new study.
The study explores the concept of chronotype, which refers to a person’s natural tendency for sleeping and waking at certain times. Night owls, or people with a late chronotype, tend to sleep and wake later than early birds, also known as larks. Although one cannot easily change their chronotype, adjusting one’s lifestyle to match it can be beneficial, according to Ana Wenzler of the University Medical Center Groningen in the Netherlands, the study's lead author.
Over a span of ten years, researchers analysed cognitive test performances of nearly 23,800 individuals. The results, published in The Journal of Prevention of Alzheimer’s Disease, revealed that people with an evening chronotype experienced faster cognitive decline than those with a morning chronotype.
"Unhealthy behaviours such as smoking, alcohol consumption, and poor dietary habits tend to occur more frequently in the evening," said Wenzler. "In our study, we observed that evening people smoked and drank more and exercised less. About 25 per cent of the cognitive decline risk we identified can be attributed to smoking and poor sleep."
The study further highlighted that higher-educated individuals showed a greater decline in cognitive ability when aligned with a delayed sleep-wake rhythm. Specifically, a one-hour delay in the sleep-wake cycle was associated with a 0.8-point decline in cognitive performance per decade.
Wenzler suggested this cognitive dip may be linked to disrupted sleep patterns. Evening chronotypes often need to start work early, leading to insufficient sleep and inadequate rest for the brain.
She also explained that chronotypes shift with age. "Children are naturally morning people. This changes during puberty, when people tend to become evening types. In most individuals, the tendency begins to shift back towards a morning pattern by their 20s, and by age 40, most are morning people again," she said.
However, not everyone follows this trajectory. Some people remain evening types throughout their lives, deviating from the general pattern. Wenzler recommended avoiding fighting against one’s biological rhythm whenever possible.
"You can try to go to sleep earlier, but if your body hasn’t started producing melatonin — the sleep hormone — yet, it simply won’t work. Your body isn’t ready for sleep," she explained. "If avoiding this mismatch isn't possible, the brain lacks sufficient rest, and the individual becomes more vulnerable to unhealthy habits."
She concluded that more consideration should be given to evening chronotypes, particularly in workplace settings. "It would be beneficial if evening people who are now expected to start work early had the option to begin their day later," Wenzler said.
With PTI inputs