Older people who nap during the day are more likely to be diagnosed with heart disease or cancer, scientists say.
A study of almost 11,000 people found those who were sleepy during the day were two and a half times more at risk of developing heart illnesses.
They faced double the risk of cancer and were also more than twice as prone to diabetes and high blood pressure. Arthritis was one and a half times as common.
The US researchers suggested families pay attention to their grandmas and grandads who nod off regularly because it could be an early warning sign of a serious medical condition.
Older people who nap during the day are more likely to be diagnosed with heart disease or cancer, research by Stanford University, California, shows
The study looked at hypersomnolence, a condition defined as excessive daytime sleepiness even after having seven or more hours of sleep. It can be debilitating for some, affecting the way they perform at work and in other routine activities.
It has previously been linked to dementia, and the latest research suggests it can flag up more of the world’s major killers.
Lead author Professor Maurice Ohayon, a psychiatrist at Stanford University, California, said: ‘Paying attention to sleepiness in older adults could help doctors predict and prevent future medical conditions.
‘Older adults and their family members may want to take a closer look at sleeping habits to understand the potential risk for developing a more serious medical condition.’
His findings presented at an American Academy of Neurology meeting in Toronto, Canada, were based on 10,930 individuals.
A third (34 per cent) were 65 or over. It is not clear what age bracket the rest of the participants fell into.
Participants were interviewed twice over the phone, three years apart. In the first and second interviews almost a quarter of over 65s met the criteria for excessive sleepiness. Of those, four in ten said it was a chronic problem.
Rates of heart disease rose 2.5 times among participants who reported daytime sleepiness both times.
What’s more, cases of diabetes and high blood pressure were 2.3 times higher in this group – and twice as many had been struck down by cancer.
For instance, of the 840 people who reported sleepiness at the first interview 6.2 per cent developed diabetes and 2.4 per cent cancer.
This was compared to 2.9 per cent and 0.8 per cent of those who were never drowsy during the day.
People who complained of sleepiness only on the second occasion were also 50 per cent more likely to have diseases of the musculo-skeletal system and connective tissue such as arthritis, tendinitis and lupus.
The results remained after other factors which may cause daytime sleepiness were taken into account, such as gender and sleep apnoea – which causes snoring by interrupting breathing. Insomnia is more frequent in women.
Professor Ohayon said: ‘The results suggest hypersomnolence in the elderly individuals can be an early sign of a developing medical condition.
‘Physicians need to pay closer attention to their patients reporting hypersomnolence.’
A limitation of the study was that it relied on participants’ memories, rather than monitoring their sleep length and quality and daytime sleepiness in a sleep clinic.
The study was observational, therefore the researchers cannot say poor sleep causes chronic conditions.
However, their findings do not come as a surprise. Problems with sleep have shown to have profound effects on health time and time again.
A lack of sleep, when a person does not sleep for the recommended seven to eight hours a night, and excessive napping have both been shown to have adverse health consequences.
Two years ago a study of older people in the US with disturbed sleep, leading to daytime snoozing, were more likely to have the first traces of Alzheimer’s disease.
Brain scans found over a quarter had abnormal amounts of a rogue protein called beta-amyloid that kills neurons.
An earlier US analysis of 2,000 elderly people showed the risk of a stroke was up to four times higher in those who had a habit of nodding off during the day.
Experts say the health benefits of sleeping for eight hours at night are very different from getting the same in hourly increments during daytime naps.
This is because of the effect it has on our body clock, or circadian rhythm, which tells us when to sleep and when to wake.
An example of the impact of altered sleep patterns are shift workers, who are more likely to report ill health, have a higher average BMI (body mass index) and increased incidence of chronic diseases such as diabetes.