Newswise — It’s that time of the year, when people walk out of air-conditioned buildings into a “sauna” that fogs glasses and creates instant beads of perspiration on their foreheads. Besides the obvious discomfort, excess heat can take a major toll on your health.

While heat-related illnesses are largely preventable, 7,233 Americans died from heat-related illness from 1999 to 2009, according to a 2013 Centers for Disease Control and Prevention (CDC) report. In 2011, 42 Texans died from heat, the highest number in the United States that year.

For populations such as seniors, children or people who work outdoors, it’s especially dangerous.

“One of the biggest differences for seniors is that they have lost the ability to perspire as naturally as younger people do. They’ve lost the ability to lower their body heat well,” says Richard Bradley, M.D., professor of emergency medicine at McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth).

Stifling heat causes the body’s temperature control system to overload. The body normally cools itself by sweating, but under too much heat stress, sweating isn’t enough. That’s when a person’s body temperature rises rapidly, which could lead to damage to the brain and other vital organs. Symptoms of heat exhaustion include heavy sweating, weakness, clammy skin, nausea and vomiting. Heat stroke is when the body temperature rises to above 103 degrees, and its symptoms include a rapid pulse, hot, dry skin and possible unconsciousness.

Cognitive changes or behavior changes can also mean that seniors are not reacting to their environment, Bradley says. They may not know to take a sweater off or move into the shade. Looking at someone’s skin is probably not the best way to determine if they are experiencing heat exhaustion or stroke. Bradley recommends keeping an eye out for a change in mental status, such as confusion.

“Seniors don’t have the mechanisms to protect themselves. A lot of older adults, if they’re on certain medications, are kept in a dehydrated state. We don’t realize how much their body uses up fluid when they’re trying to compensate in the heat,” says Elda Ramirez, Ph.D., R.N., professor of clinical nursing in the Department of Acute and Continuing Care at UTHealth School of Nursing and member of UTHealth’s Consortium on Aging.

Many seniors have chronic diseases such as diabetes or cardiovascular disease, so when a heat wave comes, that increases the load on their hearts, says Kai Zhang, Ph.D., assistant professor in the Department of Epidemiology, Human Genetics and Environmental Sciences at UTHealth School of Public Health, who studies heat and health.

Zhang has been studying how extreme heat affects elderly mortality in different regions in Texas. What he found was a significant increase in elderly mortality rates in El Paso and some counties in northern and central Texas.

“Air conditioning is the most simple and efficient prevention strategy to prevent heat-related illness. In Houston, we know the prevalence of air conditioning is around 97 percent, but it’s probably lower in the north because it’s not as hot and humid as it is in Houston,” Zhang says.

So while Houston has adapted to searing temperatures, in comparison only 76 percent of residents in Chicago have air conditioning, leaving them more exposed to heat-related illness.

A notable finding from Zhang’s research was the identification of a lag effect on seniors who had been out in the heat.

“If we observed an extremely hot day — one that was in the 90th percentile for that county — then it was highly likely that for the next 10 days, there would be a significant impact on elderly mortality,” he says.

During a heat wave, some seniors might get sick right away but others could get sick the next day or several days later. There is some delayed effect that can last up to 10 days.

Children are also at greater risk since they are considered more vulnerable to environmental hazards and are dependent on others. Infants especially are more susceptible to heat-related illness due to their high metabolic rates and inability to remove excess clothing and blankets.

Leaving a child in a hot car is one of the most terrifying scenarios a parent can experience because of how quickly things can go wrong. A recent incident in Houston showed how devastating this can be. A 3-year-old boy died after climbing into a hot car to find his toy. When he was found 30 to 45 minutes later, he was already in cardiac arrest.

“Children don’t have the ability to carry out behaviors that will move them away from hot environments. Young children, particularly if in a car by themselves, aren’t going to be able to get out without assistance. They don’t have the ability to perspire as well as older children,” Bradley says.

When taking seniors or children to an outdoor event, safety precautions must be considered.

Ramirez recommends scoping out whatever location you may be bringing your family member. Be aware if the person you are taking care of can tolerate that type of journey. If you’re going to an amusement park, but sure he or she has a place to cool down. Ask this question: Is my family member able to tolerate this activity?  Be honest about the answer and adjust accordingly.

Also, plan your activities around the coolest time of the day and don’t wait until you are thirsty to drink water — stay hydrated all day.

Obviously, outdoors workers are at high risk for succumbing to heat. Recently, a worker who was repairing a large-scale electronic sign in Houston suffered heat exhaustion. He was rescued from the 50-foot-high platform by the fire department and taken to a local hospital for treatment. Officials say temperatures had gotten up to 120 degrees inside the sign.

“Anyone who’s working outside, whether in construction or agriculture, is always at risk.  It is possible to stay safe if you have adapted or prepared for the weather, but it’s easier if you do it every day and you know how to take care of yourself in those conditions,” Bradley says.

In a study of migratory and seasonal farmworkers in Colorado, Zhang found that migratory workers were 88 percent more likely to visit a clinic on hot days than seasonal workers.

“Migratory workers are more susceptible to heat-related health issues for several possible reasons. They tend to have poorer living environments, including a lack of air conditioning; suffer from poverty, which has been linked to a higher risk of vulnerability to heat; and may lack family support for prolonged periods of time. Also, their immigration status may make them more vulnerable to labor abuses,” Zhang says.

Ramirez suggests agricultural workers start their day early to avoid the hottest time of the day. Wearing thin cotton clothes with long sleeves can help to keep the sun at bay, and the material can cool workers down when it gets wet. She also advises they eat something in the morning that will help replenish all the energy being burnt.

“In the city, it’s different because they try to get done by 5 p.m. I advise managers to have water stations close by and for workers to take hourly breaks in a cool area,” Ramirez says.