Photo/Illutration Some pedestrians are seen holding umbrellas to block out the sun in front of JR Tokyo Station on July 9. (Kayoko Sekiguchi)

A new study found that diabetics are 1.4 times more at risk of heat stroke than non-diabetics, and that men in their 30s to 50s who are in the prime of their working lives should be particularly careful.

Even in Hokkaido, the northernmost prefecture with a relatively cooler climate, researchers found that there was an increased risk of heat stroke, depending on age.

“Diabetics should first be aware that they may have difficulty feeling the heat and that their risk increases even when the temperatures are not as high, so they should take action as soon as possible,” said Akimasa Hirata, professor of biomedical engineering at the Nagoya Institute of Technology, who led the research group.

In the study, the researchers at Nagoya Institute of Technology analyzed medical fee statements to assess their heat stroke risk.

It has been previously reported that diabetic patients are more susceptible to heat stroke because of their lessened capabilities to perspire and regulate their body temperatures. In addition, they are less likely to notice thirst and heat sensations.

However, such studies were small in scale. The research group therefore utilized a nationwide insurance database.

The risk of heat stroke was examined by comparing approximately 188,000 diabetics and 750,000 non-diabetics matching gender, age and region.

In a follow-up after about seven years, it was found that 800 diabetics and 2,270 non-diabetics suffered heat stroke.

The analysis showed that overall, the risk of heat stroke in diabetics was 1.41 times greater than in non-diabetics.

The risk for men in their 30s to 50s was above average, ranging from 1.69 to 1.41 times higher.

For both men and women, there was no clear statistical difference for those under 30 years of age.

By region, in Hokkaido, the risk was 1.94 times higher for diabetics in their 40s and 50s.

This may be due to a delay in the body's acclimation to the heat and the lower availability of air conditioners.

Diabetics in their 40s and 50s living in the Kinki, Kanto and Chubu regions had a 1.84 to 1.42 times higher risk of heat stroke, a clear statistical difference.

In the Kinki and Chubu regions, the rate was 1.96 to 1.63 times higher among patients in their 20s and 30s.

For Tokyo and Osaka, the researchers also examined the relationship with the daily temperature.

As a result, even on days when the maximum temperature fell below 30 degrees, which is considered a relatively low risk for heat stroke, diabetics tended to be at higher risk.