Hot tubs vs. kids' health safety: Here are some facts

My local YWCA recently enacted a new rule: No kids under age 15 allowed in the hot tub. It was a blow to one of my family's favorite winter activities. On cold days, my kids play in the pool until they're shivering. Then they sit in the hot tub until they're warm enough to jump in the pool again. And repeat.

I talked to a lifeguard, who told me hot tubs “just aren't very good for young children.” Later, a manager elaborated. The YWCA had dealt with overheating incidents among kids at all three of its sites, he said. Families had been ignoring the previous policy of a five-minute hot-tub limit for 5- to 11-year olds. And the new cutoff would match hot-tub rules at other health clubs around the state.

Dismayed, I dug into the science on hot water and health, especially for kids. If there was evidence of harm, I figured I'd explain the rules to my kids. If not, maybe I could fight the spread of kid-banning hot-tub policies.

What I found was not a simple answer. Children, in some ways, respond to heat differently than adults do. But contrary to common belief, kids (beyond the baby stage) can tolerate heat just as well as the rest of us. When it comes to hot tubs, specifically, data is scarce to nonexistent. Studies simply haven't been done to analyze how likely kids are to overheat in them.

Still, the experts I talked to agreed that, at least from a health perspective, it's fine to let kids soak — in moderation and with supervision. “I certainly wouldn't say that children should not go in a hot tub,” says Bareket Falk, a pediatric exercise physiologist at Brock University in St. Catharines, Ontario. “That, I would not say.”

Overheating is dangerous for anyone. A rise in core temperature can lead to heat-related illness, such as heat exhaustion and heat stroke. At extreme levels, symptoms can include confusion, seizures, organ failure and death.

To avoid those consequences, our bodies have strategies for cooling off. One is to sweat, which cools through evaporation. Another is to increase blood flow to the skin by boosting cardiac output with a faster heart rate and widened blood vessels, among other mechanisms. Besides causing redness, that circulation strategy allows more heat to dissipate off the body's surface.

Hot tubs add a few complications. Submerged in hot water, sweat can't evaporate. At the same time, dilated blood vessels accelerate the absorption of heat, says Chris Minson, an environmental physiologist at the University of Oregon in Eugene. As a result, our bodies heat up more quickly and have more trouble cooling off in hot water than on hot days, in hot yoga classes or even in dry saunas.

Health risks of hot tubs are most acute for people with cardiovascular conditions who might not be able to handle a sudden rise in heart rate, Minson says, though people who are cleared to exercise can generally use a hot tub. Pregnant women are also advised to avoid overheating to prevent decreasing blood flow to the placenta and fetus, though he adds that a quick soak is likely OK.

“Truthfully, if a woman gets in the hot tub for a short period of time and doesn't feel too hot, she's going to be fine,” he says.

In the general population, regular hot-tub use may impair male fertility, but only temporarily, according to some evidence, and data is limited on the link. Lightheadedness and fainting can also follow a hot soak because blood pressure drops upon emerging. Fainting itself is not necessarily harmful or a sign of a bigger health issue, but people can get injured when they fall.

So, what about kids? The idea that young people are more vulnerable to hot tubs may have come from observations about the unique ways that small bodies regulate temperature, Falk says. With more surface area relative to body mass, kids absorb and lose heat more quickly than adults do, which makes them quicker to get chilled in cold water and hot in hot water. To maintain their body temperatures, she adds, kids sweat less than adults do, and they more readily increase blood flow to the skin.

But thermoregulating differently doesn't mean kids are necessarily worse at doing it. Data do not show higher rates of heat-related injuries in general, even during heat waves, Falk says. And kids may even have an advantage in some situations. With their larger surface area, they are more efficient at sweat-evaporation, she and colleagues found in a 2008 review.

Saunas, too, are safe for healthy children above age 2, according to a review of research that was published in 1997 but is, Falk says, still valid. In countries such as Finland, parents start bringing babies as young as 4 months old into saunas, though studies have yet to include infants. There is evidence children have an elevated risk of fainting in saunas.

Children do not seem to be suffering disproportionately from health consequences of hot tubs, either. In a 2009 analysis of more than 81,000 hot-tub related emergency-room visits between 1990 and 2007 (the latest data available, says study author Lara McKenzie of Nationwide Children's Hospital in Columbus, Ohio), researchers found that people over age 16 were more likely than younger people to show up at hospitals because of overexposure to heat.

Overall, 73 percent of hot-tub injuries occurred in people ages 17 and older. Slips and falls were the most common cause of injury, while lacerations and soft-tissue injuries topped the list of diagnoses. It is also possible to get bacterial infections from hot tubs.

That doesn't mean that hot tubs, like swimming pools, are good places to let kids run free. The 2009 study (which was based on data collected from the U.S. Consumer Product Safety Commission's National Electronic Injury Surveillance System), found that more than 700 kids died of hot-tub accidents between 1990 and 2007. Incidents included trapped hair and body parts, disembowelment and drowning. Near-drowning was the most common cause of nonfatal injury.

The Centers for Disease Control and Prevention recommends keeping kids under 5 out of hot tubs, though its fact sheet doesn't cite heat as the reason. The CDC also suggests sniffing for strong chemical smells before getting into a hot tub, avoiding swallowing hot-tub water and keeping hot-tub temperatures at 104 degrees or lower.

For kids and adults, Minson says, it's a good idea to take breaks from the hot tub if you feel uncomfortably hot or tired. But, he says, growing evidence suggests that hot tubs and saunas can have benefits for cardiovascular and metabolic health, independent of exercise. After exercise, his research suggests, hot tubs may help boost heat tolerance and improve performance. “We're actually pushing people to use hot tubs more,” he says.

My YWCA is not showing signs of budging on its policy.

The age 15 cutoff “appears to be a standard that the health and wellness industry is adapting,” the manager wrote in an email. “It most likely stems from several factors, including concerns for the health of youth in the aquatics area.”

I am not overly concerned. When it's up to me, I'm going to continue to let my kids, ages 6 and 11, soak in hot tubs at less-strict facilities, like hotels. As soon as we get hot, we'll jump back in the pool.

“There are risks for sure, but they're way overstated in the signs you see,” Minson says. “Common sense usually prevails over all that.”