Research has shown that poor sleep is a risk factor for developing chronic disease, and that aging often involves a decline in sleep quality and quantity. However, most sleep studies have used a single measure of sleep quality taken at a single point in time. This study instead assessed multiple indicators of sleep, and looked at how they changed over time, to see if they contributed to risk of developing chronic physical and mental health conditions with age.
Data from almost 3700 MIDUS participants were collected at two time points (Time 1 & 2) about a decade apart. Participant self-reports were used to assess several dimensions of sleep at both time points:
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- Insomnia: was defined as often or almost always having trouble falling asleep, staying asleep, or waking up too early.
- Duration: short sleepers reported 7 or less hours of sleep a night, optimal sleepers 7-9 hours, and long sleepers 9+ hours.
- Efficiency: falling asleep in less than 30 minutes was considered efficient.
- Daytime tiredness: how often participants reported not feeling rested during the day.
- Napping: how many naps participants took during a week.
- Regularity: reporting more than an hour difference in total amount of sleep on workdays vs. non workdays was considered irregular sleep.
The study revealed four sleep types common at both time points:
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- Good sleepers: had optimal sleep health across all sleep dimensions.
- Insomnia sleepers: were characterized by those who reported frequent insomnia symptoms (trouble falling asleep, staying asleep, or waking up too early), who slept 7 or fewer hours a night (short sleep duration), took longer than 30 minutes to fall asleep (low sleep efficiency), and were often tired during the day.
- Nappers: were characterized by mostly good sleep but took frequent daytime naps (4+/week).
- Weekend catch-up sleepers: slept less than 7 hours on work days, but 9+ hours on non-work days (irregular sleepers).
Researchers then looked at how these sleep types related to the following:
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- Chronic illness: how many of 30 chronic conditions participants reported having in the past year.
- Common chronic disease categories: participants were categorized as to whether they had cancer, diabetes or high blood sugar, cardiovascular diseases (such as high blood pressure, angina, heart attacks), or respiratory diseases (such as asthma, bronchitis, tuberculosis).
- Frailty: measured by symptoms such as weight loss, exhaustion, slowness, and muscle weakness.
- Depressive symptoms: whether participants felt sad, blue, or depressed for at least two weeks in the past year.
Results showed that, when compared to consistently good sleepers at Time 1 & 2, nappers and insomniacs were most at risk:
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- Those who were insomnia sleepers at Time 1 and/or 2 and good sleepers at Time 1 who became nappers at Time 2 were most at risk of having more chronic conditions at Time 2.
- Consistent insomniacs (at both time points) had higher risk for cardiovascular disease (72% higher), diabetes (188% higher), frailty (68% higher), and depression (95% higher).
- Consistent nappers were 128% more likely to have diabetes.
- Good sleepers who became insomniacs had increased risk for depression (89% increase) and frailty (108% increase).
- Good sleepers who became nappers were at 62% higher risk for frailty.
- Nappers who became insomniacs were more likely to become frail (456% more) and get cancer (45% more).
- Weekend catch-up sleepers who became nappers were 137% more likely to have diabetes.
Researchers also looked at who was more likely to have each sleep type:
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- Younger adults were more likely to be weekend catch-up sleepers.
- Older people and retirees were more likely to be nappers.
- People who were unemployed were more likely to be insomniacs, perhaps because of stress.
- Those with more education were less likely to be insomniacs.
Data also showed that most participants (77%) remained in the same sleep type between Time 1 and 2. The percentages were even higher for the more unhealthy sleep types: over 90% of insomnia sleepers remained insomniacs, and 97% of nappers remained nappers. Weekend catch-up sleepers were the most likely (73%) to transition to a different sleep type at Time 2, but, unfortunately, 60% transitioned to the less healthy napper or insomnia types.
These results suggest the need for multiple interventions to improve sleep. Treatments could vary depending on a person’s sleep type, with nappers and insomniacs the most in need of support to prevent future chronic illness. Targeting treatment for those who are unemployed or have less education among the insomnia sleepers and for retirees and older adults among nappers, may bring the best results.
More research is needed to better understand the consequences of napping, as there may be times when napping is beneficial to catch up on lost sleep. It may also be that napping is more problematic among older adults as a result of age-related changes in the body. Using questionnaires allowed for a larger sample size in this study, but future research could also incorporate objective sleep data such as measured by watches worn by participants. More research looking at the underlying mechanisms of how poor sleep contributes to chronic conditions is also needed.
Source: Lee, S., Smith, C. E., Wallace, M. L., Buxton, O. M., Almeida, D. M., Patel, S. R., & Andel, R. (2024). Ten-year stability of an insomnia sleeper phenotype and its association with chronic conditions. Psychosomatic Medicine, 86(4), 289-297. https://doi.org/10.1097/PSY.0000000000001288
Read the full article at: http://www.midus.wisc.edu/findings/pdfs/2807.pdf