Putting Out Fires Hurts Firefighters’ Hearts

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As the temperature outside rises, our bodies make adjustments to keep our internal temperature constant to prevent us from overheating through a process called thermoregulation. This includes bodily functions such as sweating and widening of the blood vessels (vasodilation). When we sweat, perspiration evaporates from our skin to cool us down. When the blood vessels under our skin widen, our heart pumps more blood to our skin, which releases more heat from our inner body.

Our bodies are constantly working to hold a steady core temperature around 98-100 degrees Fahrenheit (F). This allows our organs to function properly. But when the temperature outside is extremely hot, our temperature can start to rise. A person with a body temperature above 104 degrees can develop heat stroke. This can cause dizziness, difficulty breathing, confusion, seizures or loss of consciousness. Brain and heart damage—sometimes permanent—can occur when body temperature climbs above 107 degrees F.

Too much summer heat can be unhealthy for everyone, but it can be especially dangerous to firefighters. The incidence of fires increases in the U. S. during the summer months. Firefighters fight almost twice as many fires in the summer compared to the rest of the year. On top of dealing with the extreme heat (sometimes over 700 degrees F!), these first responders face extreme physical exertion, mental stress and smoke inhalation on the job. All of these factors together can place firefighters in immediate danger of heat exhaustion, heatstroke and heart problems. In fact, firefighters are up to 136 times more likely to die from coronary artery or heart disease during or soon after they suppress a fire.

In a study published in Circulation last month, researchers may have uncovered several reasons why putting out fires puts firefighters at risk for heart disease. They discovered that a single, 20-minute session of fire simulation training—where healthy firefighters were exposed to physical activity in the extreme heat (about 755 degrees F)—was enough to injure their blood vessels, even though the firefighters’ core body temperature never reached above 101 degrees F. The problem: Although the firefighters’ bodies did keep their core temperature within a healthy range, their blood vessels did not relax properly immediately after the training. Also, as a result of the training, the firefighters’ blood clotted more easily. Damaged blood vessels and increased clotting of the blood can be very harmful to the heart and sometimes can lead to a heart attack.

This research shows us that even when we are able to keep our body temperature from getting too high, there are hidden dangers of being physically active in extremely hot temperatures. So keep your heart healthy this summer and don’t overexert yourself while outdoors!

Dao Ho, PhD

Dao H. Ho, PhD, is a biomedical research physiologist at Tripler Army Medical Center. The views expressed in this blog post are those of the author and do not reflect the official policy or position of the U.S. Department of the Army, U.S. Department of Defense or the U.S. government.

When’s the Best Time to Eat? Your Body Clock Knows

 

Two teenager girls, sisters, eats fastfood on the street

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The American Heart Association recently released a statement suggesting that when and how often you eat could affect your risk for developing heart disease and stroke. Until now, the focus on diet has been primarily about how much and what you eat. This news—that the time of day you eat may also be important—could change the way people are able to manage their health.

Our bodies have natural daily patterns called circadian rhythms that occur roughly over a 24-hour cycle. Many biological processes are driven by circadian rhythms, including when you go to sleep and wake up, your body temperature, heart rate, blood pressure and the release of various hormones. A “master clock,” a tiny group of cells called the suprachiasmatic nucleus (SCN), located in the hypothalamus area of the brain manages circadian rhythms. This master clock is mostly controlled by changes in light.

Every cell in the body also has its own internal clock called a “peripheral clock.” Peripheral clocks make sure all of the cells’ functions are coordinated with the master clock. Animal studies show us the importance of keeping peripheral clocks in sync with the brain’s master clock. For example, when the peripheral clock in a mouse’s heart is disrupted, the mouse develops heart failure and dies at a much younger age than normal mice.

Unlike the master clock, peripheral clocks are more responsive to the availability of food than changes in light. As a result, eating at the “wrong” time of day could shift the rhythms of the peripheral clocks so they are out of sync with the master clock. For example, shift workers who work in the middle of the night are active when they would normally be asleep and eat at times when their body doesn’t expect food. They are at much greater risk for being overweight, becoming insulin resistant and developing cardiovascular disease because their master and peripheral clocks are likely to be out of sync.

Research in mice has shown that if they consume a high-fat meal at the end of their active period (the equivalent of a high-fat dinner for humans) they gain more weight, develop insulin resistance and have impaired cardiac function compared to mice that eat the same high-fat meal at the beginning of their active phase (breakfast).

Studies in people suggest that eating meals late in the day is linked to negative health effects, but a direct relationship has not been shown. Nevertheless, if when you eat is just as important as what you eat, it might not hurt to eat your larger meals earlier in the day if you can.

 

John Chatham

John Chatham, DPhil, is a professor of pathology and director of the Division of Molecular and Cellular Pathology at the University of Alabama at Birmingham.

Go Ahead, Wear Your Heart on Your Sleeve!

Jousting Competition

A jousting knight wears his heart on his sleeve. Credit: iStock

In medieval times, a jousting knight would wear the colors of the lady he was courting tied around his arm. Hence, the phrase “Wear your heart on your sleeve” was born. Today, we use this romantic phrase to describe someone who expresses their emotions openly. How applicable that ancient phrase really is to maintaining a healthy heart!

In a landmark paper, a group of scientists discussed how stress and social interactions with others affected the health of the heart. It is well-known that stress is a major factor in the development of heart disease. This is because stress is a double whammy: It activates the “fight-or-flight” nervous response, and it causes inflammation in the cells that line blood vessels. Both of these events can damage blood vessels in the heart.

Research shows that positive social interaction expressing emotion is important for heart health. Support from a spouse or partner, friends or other groups can reduce stress and help you stick to a healthy diet and exercise program to minimize your risks.

Heart disease is the leading cause of death worldwide, with annual deaths creeping up to 24 million. Reducing stress and anxiety is an important aspect of keeping your heart healthy. Exercise, yoga, meditation and even deep breathing can promote a sense of calm when tensions mount. Try running or yoga with a friend or join an exercise class to keep you on track for a healthy heart. Go ahead, wear your heart on your sleeve—it’s good for you!

February is American Heart Month. You can find more information about keeping your ticker ticking on the American Heart Association’s website.

Audrey Vasauskas

Bring on Winter! (But Stay Safe and Healthy)

 

girl playing on a winter walk

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Winter officially begins next week with the winter solstice—the day of the year with the fewest hours of sunlight—on Dec. 21. With the cold weather and shorter days, you might be tempted to curl up under a blanket until the spring thaw. Whether you plan to hibernate or get outside to enjoy the chill, we’ve got some good reads about how our physiology responds to the cold weather.

Check out these throwback posts featuring cold weather tips to help you stay safe and healthy during the coldest months:

Have fun, be safe and take note of how your body adapts to the season!

Stacy Brooks and Erica Roth

 

 

Can Alcohol Cause Irregular Heartbeat?

red wine

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Alcohol and heart health have a complicated relationship. Recent research suggests that moderate drinking may reduce your risk of stroke. But for some people, even one or two drinks a day may increase the risk of a form of heart disease called atrial fibrillation (AFib).

AFib is an irregular heartbeat of the two upper chambers of the heart (atria). During an episode of AFib, the atria beat quickly and out of synch with the lower chambers of the heart (ventricles). This irregular pattern can cause blood to clot in the heart, which also increases the risk of stroke.

A recent study published in the Journal of the American Heart Association suggests that over time, moderate alcohol consumption may cause the left atrium to become larger. The enlargement of the heart chamber can lead to AFib in some cases. This is one of the first studies to show in a large population of humans that structural changes in the heart can cause AFib. Previously, AFib had been thought to arise as a result of problems with the electrical impulses in the heart.

For most people who follow a heart-healthy diet, exercise and don’t have high cholesterol or high blood pressure, the occasional drink probably won’t hurt or lead to AFib. However, it’s a good idea to be aware of the alcohol-related heart disease risk as office parties and family gatherings get into full swing this holiday season.

Learn more about atrial fibrillation from the Mayo Clinic.

Erica Roth

Looking for a New Physical Challenge? Try a Mountain Ultra-Marathon

Idyllic Alps Valley

The Aosta Valley in Italy where the Tor des Geants is held. Credit: iStock

Of all the extreme endurance races out there—such as the Ironman triathlon or 50- or 100-mile marathons—the Tor des Géants ultra-mountain marathon may be the most extreme. The course is 205 miles long on the rugged terrain of the Italian Alps with a cumulative elevation gain of 24,000 feet. Participants have 150 hours, little more than six days, to complete the course. These feats of ultra-endurance are fascinating for scientists because they showcase how the heart adapts when pushed to the limit. Previous studies have found that after 3- to 15-hour races like marathons and the Ironman triathlon, the heart doesn’t pump as well, a condition referred to as exercise-induced cardiac fatigue. A group of French researchers looked at what happened to the heart after running for over 100 hours in the Tor des Géants. They were surprised to find that unlike with marathons and triathlons, heart function improved after the ultra-mountain marathon race.

During a heartbeat, the heart fills with blood and then squeezes together to push out the blood. In situations in which the body constantly needs more oxygen, such as with exercise, the amount of blood filling the heart is one signal that tells the heart to keep beating harder. The more the heart fills, the stronger the heart contracts.

This study found that the runners’ hearts filled more during each heartbeat. The researchers think it’s because the amount of plasma, which is the liquid portion of blood, increased, raising the overall amount of blood in the body. But why it increased is not clear. Fluid intake could be one factor, says Michael Joyner, MD, an exercise physiologist not involved in the study, in a podcast. Runners in ultra-long races pay extra attention to staying hydrated and often maintain or gain weight from the extra fluids, he says. Stéphane Nottin, PhD, the lead investigator of the study, wonders if inflammation from the extreme physical stress or greater retention of sodium (the kidneys use sodium to absorb water) is also involved.

“Physiology has a long history of expedition-led investigations—whether it’s high altitude, desert—and this paper follows in that wonderful tradition,” Joyner says. Other current ongoing studies in this spirit include a Mount Everest climb to examine cognitive decline at low oxygen levels and a study on the heart of a swimmer swimming across the Pacific.

 

Maggie KuoMaggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.

 

The Anti-Aging Cure May Be in Your Medicine Cabinet

Older dog - Younger dog

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Rapamycin, a drug used to prevent organ transplant rejection, may also turn back time—in dogs at least. A study is underway to see if rapamycin can delay aging in dogs, and the puppy-like energy of one canine participant, eight-year-old Bela, gives some hope that the drug might work. Rapamycin is one of several drugs prescribed to treat other conditions that are being studied for their potential to help humans grow old without the health problems of aging. These drugs are particularly promising because they are already being used by people and are well-tolerated by the body. Other drugs being investigated include:

  • Metformin: Metformin is a commonly prescribed treatment for type 2 diabetes. The specifics of how it counteracts aging are still being debated, but the scientific community generally agrees that small doses of metformin can improve metabolic health, reduce cancer risk and lengthen lifespan. The Targeting/Taming Aging with Metformin study is currently underway to test if metformin has anti-aging effects in people, as it did in mice.
  • Aspirin: Constant low-level inflammation is considered a hallmark sign of aging, so researchers wonder if anti-inflammatory drugs such as aspirin can help. Studies have found that lifelong use of aspirin lengthens the average lifespan of male mice but does not increase maximum lifespan. No effects have been seen in female mice. Other studies in mice have shown that aspirin can improve immune, metabolic and cardiovascular health. However, aspirin also prevents blood from clotting and irritates the intestines, which can increase the risk of internal bleeding.

Researchers are also looking at lifestyle choices for their fountain-of-youth benefits, including:

  • Vegan diet: A vegan diet reduces the consumption of methionine, a nutrient abundant in eggs and meat. Eating less methionine has been shown to increase the lifespan of yeast, worms, flies and rodents. However, methionine is an essential nutrient for the body, so its anti-aging properties may be counteracted by the health effects of not having enough of it.
  • Calorie restriction: Reduced-calorie diets are a well-established method for extending the lifespan in various species, including certain strains of mice. However, in other mice strains, calorie restriction dramatically shortens the lifespan.

This detrimental effect in mice demonstrates a primary concern for testing anti-aging treatments in humans: A drug or lifestyle switch might shorten a healthy participant’s life. While it will take many years to find out if a treatment can truly increase longevity, we already know that wisdom only comes with time—and age.

Maggie KuoMaggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.

Don’t Be Cold-Hearted: Understand and Protect Yourself from the Cardiovascular Risks of Cold Weather

Shoveling Snow

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Winter storms, like those that hit the East Coast in January, are often followed by sad reports of deaths from heart attacks related to winter weather. These reports often seem to be isolated incidents, but emerging evidence reveals a clear association between winter temperatures and heart attacks, particularly severe heart attacks. Recent research demonstrated that for every 18-degree drop in outdoor temperature below 86 degrees Fahrenheit, the risk for a severe heart attack increased by 7 percent. That means the risk of a heart attack is 28 percent higher at freezing temperatures. What accounts for the increased risk with cold weather?

There are a number of factors that raise a person’s chance of having a heart attack, but many heart attacks ultimately arise from an inability to provide enough oxygen to the heart. This can cause permanent damage to the heart and, if severe enough, can lead to death. In response to cold temperatures, the heart begins to pump more blood with every heart beat, and blood vessels in the limbs narrow (constrict). These physiological responses coupled with cold weather-associated activities such as shoveling snow increase the heart’s demand for oxygen-rich blood. In healthy individuals, this demand is readily met by increasing blood flow to the heart, but this increase is often blunted in individuals with cardiovascular disease or risk factors. Men older than 55 are twice as likely as women to experience snow-related heart problems, especially if they have a family or personal history of cardiovascular disease.

How can we use this information to protect ourselves? Some practical tips:

  • Understand your own cardiovascular risk and family history.
  • Maintain your preventive health care throughout the year by staying physically active, eating a balanced diet and having annual check-ups with your doctor.
  • Dress appropriately for work and play in the cold to limit heat loss and its stress on the heart.
  • Remember that the average shovel of snow weighs at least 10 to 15 pounds. Repetitive shoveling of these loads is a dangerous level of exertion for someone with cardiovascular risk factors, so buy a smaller shovel and take regular breaks.
  • Pay attention to early signs of a cardiovascular event—chest pain, dizziness, shortness of breath—and stop immediately if they occur. If symptoms persist, seek medical attention immediately.

If knowledge is power, then the research provides the power to protect us from heart attack risk in cold weather. Think this through the next time a winter storm approaches, and spread the word to help reduce snow-related heart attacks in your community.

Shawn Bender, PhD

Shawn Bender, PhD, is a research health scientist at the Harry S. Truman Memorial Veterans’ Hospital and an assistant professor at the University of Missouri.

Does Exercising in Warm Weather Make You Fitter for Cooler Temperature?

Hot Weather Exercise

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Those who are active year-round know that summer workouts are more tiring than those done in cooler weather. The good news is that it’s not a sign that you’re suddenly out of shape. Exercising in warm temperatures is not the same as exercising in cooler temperatures and the body’s physiology has to adjust. How does the body adapt and can these changes translate to performance gains in cooler temperatures?

The body takes about 10 days to acclimate to exercising in heat. The most noticeable signs that it has adapted to warmer weather are sweating more easily and a lower exercising heart rate. Less perceptible physiological changes include greater volume of plasma—the liquid portion of the blood in which the red blood cells are suspended—less salt released through sweat and more efficient heart and muscle function.

Because these physiological adaptations improve exercise performance in heat, scientists and athletes have wondered if these changes also mean enhanced performance in cool conditions. The jury, though, is still out. A study in 2010 in the Journal of Applied Physiology reported that exercising in heat did improve exercise performance in cooler weather. A new study published last month in the American Journal of Physiology—Heart and Circulatory Physiology concluded the opposite: heat training only improved performance in hot conditions, but not temperate ones. Nonetheless, both studies show that the body can adapt to new conditions relatively quickly. So, when you find it hard to catch up when it’s hot, be patient. You’re not out of shape, it’s just your body is catching up.

Maggie KuoMaggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.

Get a Grip: What Grip Strength Can Tell Us about the Cardiovascular System

Anne Crecelius, PhD

Anne Crecelius, PhD

Most of us grab hold of something every day—the steering wheel of a car, the handle of a heavy shopping bag or the hand of a new acquaintance. Whatever we’re holding, we’ve got a grip on it.  But our grip strength can do more than help us hold on to an object. Handgrip is often used by physiologists to measure heart and blood vessel health. For example, the New York Times recently reported on a scientific article that found grip strength to be a predictor of heart attack and stroke. Researchers found that for each 11-pound decrease in grip strength there was “a 17 percent increased risk of cardiovascular death, a 7 percent increased risk of heart attack and a 9 percent increased risk of stroke.”

So, how is handgrip related to cardiovascular health? Researchers use handgrip as a technique to make muscles work so they can investigate cardiovascular responses including blood vessel expansion (dilation) during exercise. Handgrip exercise is easy to perform—most people can do it so scientists can study lots of different people. At low intensities, handgrip exercise only affects the blood vessels in the forearm and doesn’t bring in whole body cardiovascular reflexes, such as increasing heart rate, which could make the results of an experiment difficult to understand.

Many researchers use handgrip exercise to study blood vessel response during exercise. Recently, my colleagues and I showed that taking vitamin C (ascorbic acid) by mouth before exercising helped older people have greater blood flow and, therefore, oxygen delivery to their muscles while performing increasingly harder handgrip exercises. We’re not sure whether this would help with other types of exercise, but the results can help us understand one way to potentially improve exercise tolerance in older adults.

So the next time you shake someone’s hand, give it a firm squeeze. You’re working your cardiovascular system at the same time!

Anne R. Crecelius, PhD, is an assistant professor in the department of health and sport science at the University of Dayton in Dayton, OH.