Summary: People who naturally stay up late, so-called “night owls”, are more likely to experience faster cognitive decline than those who are early risers, according to a long-term study. Researchers found that unhealthy behaviors common in the evening, such as poor sleep, smoking, and drinking, may explain part of this risk.
The study showed that 25% of cognitive decline could be linked to these habits, especially among higher-educated individuals who often face early work schedules that clash with their natural rhythms. While chronotype is largely genetic, aligning daily routines with one’s biological clock may help protect long-term brain health.
Key Facts:
- Chronotype Matters: Evening types showed faster cognitive decline over 10 years.
- Behavioral Link: Risk is partly explained by more smoking, drinking, and poor sleep.
- Lifestyle Tip: Working against your natural sleep rhythm may worsen brain health.
Source: UMCG
Are you a morning or an evening person?
Those who stay up at night and go to bed late are more likely to suffer cognitive decline than morning people, UMCG research shows.
‘The good news is that you can partly influence this cognitive decline by adjusting your behaviour,’ says researcher Ana Wenzler, whose research contributes to dementia prevention.
Because we are getting older, there are more and more people with dementia. Within a large national study, the BIRD-NL project, the UMCG, together with many partners, is researching ways to prevent dementia.
‘The fact is that your brain deteriorates after the age of 40, says Wenzler. ‘We study which lifestyle or other factors can reduce the risk of dementia.’
What is your chronotype?
Wenzler’s area of research is sleep.
‘Using Lifelines data, I look at people’s sleep rhythms. Are you an early bird or a night owl? It’s hard to adjust what your biological clock – your so-called chronotype – is, but you can adjust your life to it as best you can. In my research, I looked at whether your chronotype affects your cognition through behavior.’
Based on questionnaires that Lifelines participants filled in about their sleep times, Wenzler was able to determine the extent to which people are extreme early or late sleepers, and everything in between.
She then looked at the results of a cognitive function test over a 10-year period: how did early scores differ from scores 10 years later?
More frequent unhealthy behaviour in the evening
The conclusion: evening people decline cognitively faster than morning people.
‘Unhealthy behavior such as smoking, drinking and unhealthy eating happens more often in the evening’, says Wenzler.
‘In our study, we also saw this: evening people smoke and drink more often and exercise less. 25% of the risk of cognitive decline can be explained from our research by smoking and poor sleep.’
Interestingly, the difference was found mostly in higher-educated people.
‘That probably has to do with their sleep rhythm. They are often people who have to go back to work early in the morning and are therefore more likely to sleep too short, giving their brains too little rest.’
Genetic evolution
Wenzler, herself more of an early bird a night owl, explains how people’s biological clocks are genetically altered.
‘Children are morning people. That changes when you reach puberty, when you become an evening person. Around your 20s, that gradually shifts back towards morning people for most people.
‘By the age of 40, most people are morning people again. But this is certainly not the case for everyone. In this way, evening people deviate from the norm’.
Work against your body as little as possible
There is little you can do about being an evening person. That is why Wenzler recommends working against your body as little as possible.
‘You can try to go to sleep earlier, but if your body is not yet producing melatonin (sleep hormone, ed.) it will not work: your body simply does not want to sleep yet.
‘We suspect that lower- or middle-educated people are more likely to have a job that allows them to take their sleep rhythm into account, such as a job in the hospitality industry or one with night shifts.
‘If this is not possible, your brain does not get enough rest and you are more likely to adopt bad habits. It would be nice if more consideration was given to evening people who now have to work early: for example, by giving them the option of starting later.’
Follow-up research
Meanwhile, Wenzler’s research continues.
‘We are now investigating whether evening people are more likely to develop dementia. Faster cognitive decline in middle age does not necessarily mean a higher risk of dementia. With our research, we hope to find out more about this. This will ultimately help us to be able to give people informed advice on how to try to prevent dementia.’
About this chonotype and cognition research news
Author: Joost Wessels
Source: UMCG
Contact: Joost Wessels- UMCG
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Chronotype as a potential risk factor for cognitive decline: The mediating role of sleep quality and health behaviours in a 10-year follow-up study” by Ana Wenzler et al. The Journal of Prevention of Alzheimer’s Disease
Abstract
Chronotype as a potential risk factor for cognitive decline: The mediating role of sleep quality and health behaviours in a 10-year follow-up study
Background
With rising life expectancies and ageing populations worldwide, preserving cognitive health is an urgent global priority. Chronotype could be a potential risk factor for cognitive decline, potentially through mediators sleep quality, alcohol intake, physical activity, and smoking.
Methods
This study used data from participants aged 40 years and older from the Lifelines cohort study (n = 23,798). Chronotype, assessed with the Munich ChronoType Questionnaire, was included as a continuous score of mid-point sleep corrected for sleep debt on workdays. Multiple linear regression examined the association between chronotype and cognitive decline, including moderation by age, educational attainment, and sex. The KHB-method was applied to test mediation by sleep quality, alcohol intake, physical activity, and smoking.
Outcomes
Cognition was assessed with the Ruff Figural Fluency Test (RFFT), measuring non-verbal fluency and executive functioning. Cognitive decline was calculated by subtracting the RFFT sum score at baseline from the 10-year follow-up score.
Results
Chronotype was associated with cognitive decline. Educational attainment, but not age or sex, moderated the relationship. No significant associations were observed in the low- (0.07, 95 % CI: -0.44, 0.57) or middle- (-0.41, 95 % CI: -0.88, 0.06) educational groups. In the high-educational group each one-hour increase in chronotype corresponded to a 0.80-point decline in cognition per decade (95 % CI: -1.34, -0.26). In this group, sleep quality and current smoking mediated 13.52 % and 18.64 % of the association, respectively.
Interpretation
Chronotype was associated with greater decline in non-verbal fluency and executive functioning among higher educated participants, highlighting the importance of targeted prevention strategies.
Funding
This work is part of the BIRD-NL consortium funded by the Dutch Medical Research Council, ZonMw (Dementia research program) project number:10,510,032,120,005.
