TOKYO, Aug. 2 (Xinhua) -- Health damage caused by heat-related sleep disorders in Japan's urban areas may be comparable to that of heatstroke, local media reported, citing an analysis by researchers from the University of Tokyo and other institutions.
As Japan continues to navigate the scorching summer months, the nation faces the challenge of safeguarding its citizens not only from heatstroke's immediate danger, but also from the more insidious threat of sleep disorders that can quietly undermine health and well-being.
To compare the impact of sleep disorders and heatstroke, the research team utilized the "disability-adjusted survival year," an indicator that can be used to compare losses due to death or illness in terms of years, Japan's Mainichi Shimbun reported Wednesday.
This measure calculates, for example, a "loss of three years" for 10 years of illness or disability with a severity of 0.3. The severity of sleep disorders is 0.1, which is equivalent to diabetes without complications.
The questionnaire was updated to allow for daily assessments for the analysis, which used global data to gauge sleep quality over the course of a month.
In August 2011 and July-August 2012, researchers surveyed a total of 1,284 male and female residents of Nagoya, Japan, aged 20 to 70, asking them about the quality of their daily sleep.
In order to define "tropical nights," days with a minimum temperature of 25 degrees Celsius or higher were used. Based on participant responses and daily temperatures, researchers calculated the "percentage of the population who have sleep disorders due to tropical nights." They next looked at the number of years that losses occurred.
The findings indicated that in the instance of Nagoya, losses resulting from sleep disorders were comparable to heatstroke in each of those years from 2010 to 2014.
Heatstroke specifically was estimated to cause "a loss of about 80 years" in 2010 during the country's record-breaking heat wave, while sleep difficulties were estimated to cause "a loss of about 280 years."
The Japanese Society of Sleep Research published the findings in one of its journals, reported the Mainichi.
"Sleep disorders not only lower the quality of life, but may also have the effect of decreasing efficiency during work and while learning. It is believed that when room temperatures exceed 26-27 degrees Celsius, people have trouble falling asleep and the quality of their sleep declines," Tomohiko Ihara, associate professor at the University of Tokyo and one of the team's researchers, was quoted as saying by the paper. ■