Five hours' sleep a night linked to higher risk of multiple diseases
University College London
The research, published in PLOS
Medicine, analysed the impact of sleep duration on the health of more than
7,000 men and women at the ages of 50, 60 and 70, from the Whitehall II cohort
study.
Researchers examined the relationship
between how long each participant slept for, mortality and whether they had
been diagnosed with two or more chronic diseases (multimorbidity) -- such as
heart disease, cancer or diabetes -- over the course of 25 years.
People who reported getting five hours of sleep or less at age 50 were 20% more likely to have been diagnosed with a chronic disease and 40% more likely to be diagnosed with two or more chronic diseases over 25 years, compared to people who slept for up to seven hours.
Additionally, sleeping for five hours or
less at the age of 50, 60, and 70 was linked to a 30% to 40% increased risk of
multimorbidity when compared with those who slept for up to seven hours.
Researchers also found that sleep
duration of five hours or less at age 50 was associated with 25% increased risk
of mortality over the 25 years of follow-up -- which can mainly be explained by
the fact that short sleep duration increases the risk of chronic disease(s)
that in turn increase the risk of death.
Lead author, Dr Severine Sabia (UCL
Institute of Epidemiology & Health, and Inserm, Université Paris Cité)
said: "Multimorbidity is on the rise in high income countries and more
than half of older adults now have at least two chronic diseases. This is proving
to be a major challenge for public health, as multimorbidity is associated with
high healthcare service use, hospitalisations and disability.
"As people get older, their sleep
habits and sleep structure change. However, it is recommended to sleep for 7 to
8 hours a night -- as sleep durations above or below this have previously been
associated with individual chronic diseases.
"Our findings show that short sleep
duration is also associated with multimorbidity.
"To ensure a better night's sleep,
it is important to promote 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."
As part of the study, researchers also
assessed whether sleeping for a long duration, of nine hours or more, affected
health outcomes. There was no clear association between long sleep durations at
age 50 and multimorbidity in healthy people.
However, if a participant had already
been diagnosed with a chronic condition, then long sleep duration was
associated with around a 35% increased risk of developing another illness.
Researchers believe this could be due to underlying health conditions impacting
sleep.
Jo Whitmore, senior cardiac nurse at the
British Heart Foundation said: "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.
"This research adds to a growing
body of research that highlights the importance of getting a good night's
sleep."
The research was funded by the National
Institute on Aging, part of NIH, UK Medical Research Council, the British Heart
Foundation and Wellcome.
Study limitations
Researchers used self-reported data on
sleep, which is likely to be subject to reporting bias, although using data on
4,000 participants whose sleep was measured via an electronic device confirm
the findings.
Meanwhile, data on sleep quality was
only available for those aged 60 and 70.
The Whitehall II study only involves members of the civil service, who were all employed when recruited to the study and likely to be healthier than the general population.
