Large-Scale Study Reveals The True Health Benefits of Getting Outdoors More
rael-science
Large-Scale Study Reveals The True Health Benefits of Getting Outdoors More
Getting
a daily fix of sunshine could boost your general health, with new
research linking time spent outside with better mood, improved sleep and
a lower lifetime risk of depression.
"Getting bright light in the day is as important as avoiding light at night," says psychologist
and sleep researcher Sean Cain of Monash University in Melbourne,
Australia, whose previous experimental studies have shown how artificial
light impacts sleep and circadian rhythms.
In
this new observational study, Cain and colleagues looked at the effect
outdoor light exposure had on sleep and moods in over 400,000 people in
the UK Biobank, a large study of UK adults that collects information on
everything from exercise and sleep habits to medical diagnoses and
health outcomes.
People
had been asked about their mood, medications, and time spent outdoors
on a typical day in summer and winter, amongst other things.
On
average, UK adults in the study reported spending about 2.5 daylight
hours outdoors, and early birds and morning people generally spent more
time outside than night owls.
Past research has shown that spending time outdoors and in nature has a host of health benefits, part of which might be related to natural light being the most important environmental time cue for the body's circadian rhythms.
Not getting enough of natural light could be a key factor contributing to low mood and sleep troubles which are also associated with depression, a common mood disorder and one of the leading causes of disability worldwide.
"Humans
evolved in an environment with a clear distinction between day and
night, but our modern environments have blurred this distinction," the
group explains in their paper.
These
days, people spend "most waking hours in intermediate, artificial
lighting conditions, due to reduced sunlight exposure and relatively
bright night-time light exposure."
This
can lead to disrupted sleep because light suppresses melatonin, a
sleep-promoting hormone. Previous studies from Cain and team have found
that nearly half of homes in
a Melbourne study had bright enough light to suppress melatonin by 50
percent, though individual sensitivities to artificial light vary dramatically.
In
this latest study, Cain and colleagues set about characterizing how the
amount of daylight hours spent outside relates to mood, sleep, and
health outcomes, something that has been studied less than the negative
impacts of light at night.
Getting
more light anytime between dawn and dusk was associated with better
mood and improved sleep, as well as lower risk of depression and less
use of antidepressant medications, the analysis showed.
Every
additional hour of natural light was also linked to lower lifetime odds
of depression, less antidepressant usage, and greater happiness. And
those who reported better moods and sleep with more outdoor light tended
to do so again the second time they were surveyed, on average four
years later.
Modelling
the data in this way – for a subset of some 20,000 people – allowed the
researchers to assess the effect that earlier time spent outdoors had
on later mood and sleep outcomes, while controlling for stable personal
habits.
They
also adjusted for seasonal differences, employment status, exercise,
social activities and amount of sleep – all things which can impact
mental health.
The
sunny results are somewhat expected, based on what we know about light,
nature, sleep patterns and moods, but what's encouraging to see is such
a sizeable study demonstrating the effects of spending more time
outdoors.
That
said, being an observational study that relies on people answering
questions about their daily habits and health, there may be differences
between people's actual and reported behavior. And, while this research
suggests getting outside could help to boost mood and improve sleep,
that's not so easy for everyone to do.
Soaking
up some sun in daylight hours is challenging for shift workers who are
working against normal circadian rhythms. Waking up early before work
might not be ideal for night owls and people with other chronotypes, either.
Some research suggests that defying your natural body clock is not so good for mental health, according to another recent study analysing
UK Biobank data, which found people who were misaligned from their
natural body clock were more likely to report depression and have lower
wellbeing.
What is interesting though, is the parallel between the study findings on depression risk, antidepressant use, and the growing body of evidence suggesting
that light therapy is an effective but underutilized therapy for
treating depression, especially in combination with medication.
The study was published in the Journal of Affective Disorders.
