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Those who slept 5 hours or
less or 9 hours or more, were significantly more likely to die from
cardiovascular disease over the next several years than people who logged 7
hours a night, Dr. Anoop Shankar of
the West Virginia School of Medicine in Morgantown and colleagues found.
These findings back the
results of other studies that have suggested how long people sleep may be a
key predictor of their heart disease risk, Shankar and his team report in
the American Journal of Epidemiology.
Most research on sleep duration and heart disease has been in Western
populations, aside from three studies in Japan, the researchers note. Asian
populations may have lower average body weights, different lifestyles, and
different dietary exposures, compared with those in Western populations,
that may affect their risk of cardiovascular disease, they add.
To investigate, the researchers looked at people participating in the
Singapore Chinese Health Study. The study participants, who were ethnic
Chinese living in Singapore, were enrolled between 1993 and 1998, and
followed through the end of 2006. During that time, 1,416 people died of
heart disease.
Thirty-three of the study participants said they got 7 hours of sleep a
night. People who slept for 5 or less or 9 or more hours were more likely to
have several different heart disease risk factors than those who slept for 7
hours, such as smoking and eating fewer fruits and vegetables and more fat
and cholesterol.
But even after the researchers adjusted the data to account for these risk
factors, they found that people who slept 5 hours or less were 57 percent
more likely to die of heart disease, while people who slept 9 hours or more
were at 79 percent greater risk.
Some investigators have suggested that sleeping longer may indicate
underlying poor health, Shankar and his colleagues note.
They attempted to address this fact by eliminating the first 4 years of
follow-up from their analysis, as well as excluding people with diabetes or
hypertension. In both cases the results were about the same, suggesting that
sleep duration, not ill health, was behind the relationship with heart
disease.
But when they included people with diabetes and hypertension in their
analysis, treating these conditions as risk factors, the researchers found
the link between sleep duration and heart disease mortality weakened.
This suggests, they say, that diabetes and hypertension -- both of which
have been tied to sleep duration as well as heart disease death risk -- may
help explain the relationship between sleep duration and heart disease
mortality. |