A study found that less elderly people die from heat-related illnesses on days with the "Very Hot Weather Warning" issued, and suggested the Hong Kong Observatory (HKO) introduce a warning system tailored for senior citizens to raise their alertness on heat.

The research was jointly conducted by the Chinese University of Hong Kong (CUHK)'s Faculty of Medicine and the University of Hong Kong (HKU)'s Faculty of Social Science.

The research studied the number of days with the maximum temperatures reaching 30.4 degrees Celsius or above from 1997 to 2005, and the number of elderly deaths due to Ischemic Heart Disease (IHD) and stroke, two of the most common lethal illnesses among the elderly under hot weather, on these days.

The "Very Hot Weather Warning" is only issued when the temperature is 30.4 degrees Celsius or above, research assistant professor of social science from the HKU Chau Pui-hing explained.

Among the 709 days with temperatures reaching 30.4 degrees or above, the warning was issued on 16 percent of them.

A daily average of 5.5 and 6.5 senior residents died of respectively IHD and stroke on these days, compared to 6.1 and 6.8 respectively on days without the warning issued.

"Though there is no proof of connection between the warning and mortality rate among the elderly, we believe the warning had effectively alerted the public to take preventive measures against heat stress," Chau said.

Under hot weather conditions, blood is more concentrated as a result of salt and water loss through sweating. Blood flow to the skin will also increase under excessive heat, which may overload the heart.

Jean Woo, medical professor from the CUHK, pointed out that the elderly are more prone to the influence of hot weather owing to their deteriorated ability to regulate body temperature.

"Illnesses and medications may also limit their adaptive ability," he explained.

The experts suggested the introduction of a weather warning system tailored for the elderly.

The HKO said it will thoroughly study the results of the research and review the current warning system.

"We understand the weather has a large influence on the health conditions of senior citizens, so we've been in close contact with groups that provide services to the elderly and will introduce precautionary measures against hot weather on our website," said John Leung, scientific officer of the HKO.

Chau said the elderly and their caregivers should be educated about appropriate measures, such as drinking more water and avoiding going out in the afternoon, that should be taken during hot days.

The HKO introduced the warning system in 2000. The warning is issued under certain combinations of temperature, humidity and wind speed.

(HK Edition 08/01/2008 page1)