TORONTO, Canada — A new study using data that spans 25 years has found that getting just five hours of sleep or fewer every night is associated with a higher likelihood of being diagnosed with multiple chronic diseases.
The study, which looked at the sleep duration of more than 7,000 participants at the ages of 50, 60 and 70, was published Tuesday in the peer-reviewed journal PLOS Medicine.
Those who reported regularly getting five hours of sleep or fewer at age 50 were 40% more likely to have been diagnosed with two or more chronic diseases over the past 25 years, compared to people who slept around seven hours a night, the study found.
Severine Sabia of University College London’s Institute of Epidemiology and Health and the lead author of the study, said in a press release that “as people get older, their sleep habits and sleep structure change.”
But getting seven to eight hours each night is still recommended, regardless of age.
Previous research has suggested that sleep durations above or below this recommended level may be associated with individual chronic diseases, Sabia noted.
A separate U.S. study published last week found that people who slept fewer than seven hours had a higher prevalence of heart disease risk factors, and that poor sleep is common among Americans.
Sabia and her team set out to investigate whether there was an association with less sleep and the risk of developing multiple chronic conditions, and researchers say that’s exactly what they found.
“Our findings show that short sleep duration is also associated with multimorbidity,” Sabia said.
Multimorbidity simply means the co-occurrence of two or more chronic conditions. It’s something that becomes more likely as we age, but researchers expressed concerned as it appears to be on the rise in some regions.
“Multimorbidity is on the rise in high-income countries, and more than half of older adults now have at least two chronic diseases,” Sabia said. “This is proving to be a major challenge for public health, as multimorbidity is associated with high health care service use, hospitalizations and disability.”
For this study, researchers looked at data from the Whitehall II cohort study, a database of more than 10,000 people who were employed in the London offices of the British Civil Service at the beginning of the data collection phase in 1985.
Participants then reported for followups to track their health as they aged.
They self-reported on their sleep duration around six times between 1985 and 2016. Researchers looked at this data and isolated sleep duration data given from participants when they were 50, 60 and 70 years of age, looking at around 7,000 participants in total.
They then looked at whether these participants had any chronic conditions, and, if so, when they developed.
Their definition of chronic diseases included diabetes, cancer, coronary heart disease, stroke, heart failure, chronic kidney disease, liver disease, depression, dementia, Parkinson’s disease, chronic obstructive pulmonary disease and arthritis.
Supporting previous research regarding the risk of individual chronic illnesses, sleeping for five hours or fewer at age 50 was associated with a 20% risk of being diagnosed with a single chronic illness, compared to those getting the recommended hours.
They found that those who reported regularly sleeping for five hours or fewer at the age of 50, 60 and 70 had a 30%-40% increased risk of multimorbidity compared to people who were sleeping for around seven hours a night.
They also found that those who reported five hours of sleep at age 50 were 25 per cent more likely to have subsequently died at some point across the 25-year followup period — an association that may have to do with the increased risk of chronic diseases that could be responsible for mortality, researchers explained.
But does sleeping longer than advised have any associations with chronic illness?
According to the research, it might when we’re getting up into our 60s and 70s, but perhaps not before.
When researchers looked at whether sleeping for nine hours or more had any negative health outcomes, there was an association between the incidence of multimorbidity at age 60 and age 70.
However, they found no clear association between extended sleep durations at age 50 in healthy people and multimorbidity.
If participants already had one chronic illness at age 50, long sleepers did have a 35% increased risk of developing another illness, perhaps due to underlying health conditions, researchers suggest.
Jo Whitmore, a senior cardiac nurse at the British Heart Foundation who was not involved in the research, said in the release that “Getting enough sleep allows your body to rest.
“There are a host of other ways that poor sleep could increase the risk of heart disease or stroke, including by increasing inflammation and increasing blood pressure,” she added.
“This research adds to a growing body of research that highlights the importance of getting a good night’s sleep.”
Sabia said that getting a good night’s sleep requires “good sleep hygiene, such as making sure the bedroom is quiet, dark and a comfortable temperature before sleeping.
“It’s also advised to remove electronic devices and avoid large meals before bedtime. Physical activity and exposure to light during the day might also promote good sleep.”