SINGAPORE - Contrary to popular belief among the elderly, drinking cold water is an effective way to cool the body and reduce the risk of heat stress, according to Associate Professor Jason Lee Kai Wei, who heads the Heat Resilience and Performance Centre.

The centre is based at the National University of Singapore’s Yong Loo Lin School of Medicine.

The cultural belief that the shock of cold water is bad for long-term health is not backed by science, said Prof Lee, who sees the need “to step up education to debunk myths”.

He said the elderly are especially vulnerable and must remain fit and healthy to increase their resistance to rising heat in Singapore, which reached an all-time high of 37 deg C on May 23.

Dr Tay Ruixin, a family physician at Tucker Medical, said normal age-related changes would compromise an elderly person’s thermoregulation, which functions to maintain a stable core body temperature of 37 deg C.

This can affect those as young as 60.

“Older individuals produce less sweat per sweat gland and have a lower overall sweat rate for the same heat load conditions,” said Dr Tay, on why an elderly person’s body does not cool down as effectively.

On top of this reduced ability to sweat, the elderly also have reduced blood flow to the skin, which impacts the transfer of heat from the body core to the skin for dissipation, she added.

Dr Kuan Ling Yee, a consultant at the National Skin Centre, said: “The elderly have less efficient heat dissipation, leading to a rise in core body temperature when exposed to warm weather.”

Beyond age, some medications may make individuals more sensitive to heat. Individuals with chronic illnesses may be vulnerable, as “some medications that are meant to treat the diseases may potentially compromise their thermoregulation and predispose them to a higher risk of heat injury”, said Prof Lee, who is working to uncover more about the effects of these medications on vulnerable groups.

Dr Kuan cautioned that “older individuals have decreased thirst sensation, and their kidneys’ ability to conserve sodium and water also declines with advancing age”.

For these reasons, “older people take longer to recover from dehydration”, he said.

The signs of dehydration in the elderly “may present with a change in concentration and alertness”, Dr Kuan said, adding: “At times, dehydrated elderly patients may appear lethargic or confused.”

“All older adults are encouraged to consume adequate amounts of drinks, and not merely water. Examples include soup, tea and drinks they prefer,” he said.

The physical environment is also important in preventing heat stress as the elderly “have a diminished perception of discomfort in a hot environment”, said Dr Tay. This means keeping them sheltered from direct sunlight.

There are other effective ways to cool the body down. For a dry and hot environment, Prof Lee suggests sprinkling the skin with water and turning on a fan.

“Taking cold showers is one of the ways to decrease heat strain,” he said.

Both Prof Lee and Dr Tay highlighted the importance of education to raise awareness of heat management methods and to minimise heat-related injuries as the mercury keeps rising.

“(We must) provide education for older adults and their caregivers regarding the risk of heat stress and the prevention of heat injury,” said Dr Tay.

Prof Lee said the effects of different levels of heat stress are not linear and affect individuals differently. Hence, he encourages people to consult the new heat stress advisory.

The new advisory, released on Monday by the Ministry of Sustainability and the Environment and the National Environment Agency, is in response to rising temperatures, and urges the public to be more mindful when spending prolonged periods outdoors.

The advisory follows three levels of risk of heat stress – low, moderate and high – and is based on the Wet Bulb Globe Temperature (WBGT), which takes into account the effects of humidity, sun angle and solar radiation.

It guides people on how to adjust outdoor activities based on the heat stress level, with the three focus areas of activity, action and attire.

For example, at a moderate heat stress level – where the WBGT is between 31 deg C and 33 deg C – people should take regular breaks and seek shade, drink more fluids and monitor themselves for signs and symptoms of heat-related illness. They should avoid wearing multiple layers of clothing, and use a hat or an umbrella.

The Heat Stress Advisory can be accessed via the mobile app myENV and weather information website (www.weather.gov.sg).