Photo/Illutration Residents remove snow in Okura, Yamagata Prefecture, in February 2018. (Asahi Shimbun file photo)

A new study has found that older people living in homes incapable of keeping out the cold or heat are at a higher risk of depression. 

A team of researchers showed that about 23 percent of the respondents exhibited depressive tendencies.

The team comprised Maho Iwata, a student at Tohoku University's School of Medicine, and Kenji Takeuchi, a specially appointed professor at its Graduate School of Dentistry, and other members.

"It is possible that public assistance for home renovation, such as installing heat insulation, can lead to the prevention of depression among elderly people," Iwata said.

The researchers analyzed survey data covering about 17,000 men and women aged 65 or older across Japan.

The residents were asked whether they live in homes that can keep out the cold or heat.

When the data was analyzed taking into consideration the frequency of going out and other circumstances, those who live in cold or hot homes are 1.57 times more likely to have depressive tendencies than those who don't.

By region, the value was particularly high among those living in Kyushu, the southernmost of the country's four main islands, as they are 1.8 times more likely to have depressive tendencies.

Because the survey was conducted between November and December, it is possible that the respondents were acutely aware of their cold homes.

It shows that the warmer the area they live in, the more insufficient measures are taken against the cold, indicating a particularly stronger influence of the indoor coldness.

The team measured the depression levels of the survey subjects through a set of questions developed specifically for the elderly.

The respondents scoring above a certain threshold were judged to have depressive tendencies.

The team members also asked other questions, including whether they live alone and how often they go out.

Such questions are believed to be related to susceptibility to depressive symptoms.

Previous research showed that at least 90 percent of Japanese homes fail to maintain a minimum indoor temperature of 18 degrees during the winter, which is recommended by the World Health Organization (WHO).

It is well-known that cold or hot room temperatures can lead to heart diseases, strokes and other cardiovascular and respiratory illnesses, as well as sleep disorders and other conditions.

But there had been no sufficient research done to determine a correlation between indoor temperatures and depressive symptoms or other factors as related to mental health.

The team's findings were published in Scientific Reports, a science journal.

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