Taisho Pharmaceutical Co., Ltd. conducted a survey on heatstroke and accident prevention measures during summer outdoor leisure in June 2026, targeting 484 men and women aged 20 to 60 nationwide who had participated in outdoor leisure activities within the past five years during the summer.

The survey revealed that a combined 42% of respondents answered that they had personally experienced heatstroke-like symptoms, a companion had experienced heatstroke-like symptoms, or both had experienced them during summer outdoor leisure.

During summer outdoor leisure, prolonged exposure to the outdoors can lead to unnoticed dehydration due to sweating, electrolyte loss, and rising body temperature. Therefore, it is crucial to take preventive measures beforehand rather than waiting for symptoms like thirst or fatigue to appear. Especially with the increasing number of extremely hot days in recent years, extra caution is needed for outdoor activities.

When asked about items brought for heatstroke prevention during summer outdoor leisure, the most common response was "water/tea" (330 people), followed by "sports drinks" (236 people), "hats" (229 people), "sunscreen" (194 people), and "towels" (189 people).

On the other hand, only 87 people brought "oral rehydration solutions," which are effective for efficient replenishment of water and electrolytes, and 80 people brought "ice slurry/frozen beverages," which can be used to cool the body from the inside by suppressing core body temperature rise.

While approximately 40% of people have experienced or witnessed heatstroke-like symptoms during summer outdoor leisure, preventive measures are primarily focused on basic preparations like bringing water and tea, hats, and sunscreen. Measures for heatstroke prevention, such as replenishing water and electrolytes and suppressing body temperature rise, have not yet spread sufficiently.

Furthermore, when asked about heatstroke prevention awareness for summer outdoor leisure, "frequent hydration" was the most common answer (358 people). This was followed by "avoiding direct sunlight with hats or parasols" (237 people), "drinking before feeling thirsty" (231 people), and "taking breaks in shaded or cool places" (226 people).

However, "eating a substantial breakfast before going out" was only 134 people, "getting sufficient sleep the night before" was 132 people, and "changing or canceling plans when feeling unwell" was 111 people. While hydration and sun protection are well-understood, there is a lack of awareness regarding pre-trip health management and making decisions to avoid overexertion.

Summer often involves spending long hours outdoors for activities like beach trips, river excursions, mountain climbing, camping, and outdoor events. Prioritizing enjoyment can lead to delayed recognition of heat and changes in physical condition, increasing the risk of heatstroke, dehydration, injuries, and water-related accidents. Particularly in environments with high temperatures and humidity, dehydration and rising body temperature can progress internally even if one feels "fine."

Dr. Yasushi Miyake, an expert in heatstroke and emergency medicine, provided insights on preparing for health risks before summer leisure, proper hydration and nutrition, dangerous symptoms, and first aid.

[Supervision] Yasushi Miyake, M.D., Director of the Comprehensive Heatstroke Research Institute / Visiting Professor, Department of Emergency Medicine, Teikyo University School of Medicine

An expert in emergency medicine, critical care medicine, neurosurgery, traumatology, disaster medicine, and medical education. Graduated from the School of Medicine, Tokyo Medical and Dental University. Served as Professor in the Department of Emergency Medicine and Director of the Emergency and Critical Care Center at Teikyo University Hospital. Currently serves as Director of the Comprehensive Heatstroke Research Institute and Visiting Professor in the Department of Emergency Medicine at Teikyo University School of Medicine. Holds qualifications and positions including Certified Specialist and Instructor in Emergency Medicine, and Councilor of the Japanese Association for Acute Medicine; Certified Specialist in Critical Care Medicine of the Japanese Society of Intensive Care Medicine; Councilor of the Japanese Society for Traumatology; and Certified Specialist and Councilor of the Japan Neurosurgical Society. Has extensive knowledge in emergency medicine, critical care, heatstroke, trauma, disaster medicine, and emergency medical systems, with a track record of media commentary.

Summer Leisure: The More Enjoyable the Plans, the Harder It Is to Notice Changes in Condition

During summer outdoor leisure, even when intending to take heatstroke precautions, people often find themselves in situations where risks accumulate. Activities like swimming, river play, hiking, camping, outdoor festivals, and theme parks involve prolonged outdoor exposure, combined with direct sunlight, reflected heat from the ground, high humidity, fatigue from travel, lack of sleep due to preparations, and insufficient food intake. Furthermore, the enjoyment and excitement of leisure can make it easier to overlook early signs such as thirst, fatigue, and general malaise.

Heatstroke is not simply about "feeling unwell due to heat." It occurs when body temperature rises due to exposure to hot environments, leading to the loss of water and electrolytes like sodium through sweating, disrupting the body's water and electrolyte balance. As dehydration progresses, blood volume decreases, impairing the body's ability to dissipate heat. Consequently, heat builds up in the body, potentially leading to symptoms like dizziness, headache, nausea, fatigue, and impaired consciousness.

Particular attention should be paid to the fact that dehydration and rising body temperature can occur internally even without noticeable symptoms. In leisure settings like mountains, seas, or rivers, it can be difficult to quickly move to a cool place, medical facilities may be distant, and supplies for cooling may be insufficient, making thorough preparation essential.

Moreover, children, the elderly, individuals with pre-existing conditions, those who haven't slept well the night before, and those who skip breakfast are at higher risk of heatstroke. When going out with family or friends, it is important to be aware not only of your own condition but also of the well-being of your companions.

Heatstroke Prevention Starts "Before You Go Out"

For summer leisure, it is crucial to begin heatstroke prevention measures not upon arrival at the destination, but during the preparation phase before departure.

First, check not only the weather forecast but also the Heat Stroke Risk Level (WBGT) and heatstroke alerts. Even with the same temperature, heatstroke risk significantly increases when combined with high humidity, low wind, strong sunlight, or intense ground reflection. Therefore, it is necessary to check this information on sites like the Ministry of the Environment's Heatstroke Prevention Information website and consider adjusting plans or activity times on high-risk days.

It is also important for companions to check each other's physical condition before departure. Lack of sleep, loss of appetite, fever, diarrhea, hangovers, or severe fatigue increase heatstroke risk. If there is any concern, it is necessary to make decisions that avoid overexertion, such as shortening the duration of the activity, rescheduling to cooler times, or switching to indoor facilities.

Avoiding activities between approximately 11 AM and 3 PM, when heatstroke risk is high, is also effective. Additionally, it is important to identify cool resting places in advance, such as shaded areas or indoor locations, and to pre-determine times for hydration and meals during breaks. Knowing the locations of shops, vending machines, restrooms, water sources, first-aid stations, and nearby medical facilities will help in responding calmly in case of illness or injury.

Furthermore, during summer leisure, attention should be paid not only to heatstroke but also to water-related accidents, falls, getting lost, and sudden weather changes. In mountainous, marine, or river environments, conditions can change rapidly, and in cases of illness or accidents, it may not be possible to call for help immediately.

In addition to drinks, hats, and sunscreen, prepare items such as bandages, disinfectant, cold packs, ice packs, cooling towels, regular medications, portable chargers, and a change of clothes for when you sweat. These can also be useful for initial treatment of minor injuries and for managing rising body temperature.

Decide on "Action Rules"

To avoid confusion at the destination during summer leisure, it is advisable to decide on and share "action rules" in advance. In crowded places like leisure facilities, beaches, or festival venues, communication can be difficult due to crowds and poor network conditions. Therefore, confirm meeting points and communication methods in case of separation from companions, as well as contingency plans if smartphones are unusable.

It is also important to share decision criteria for resting when feeling unwell or for canceling plans. Establishing rules such as "rest if you get a headache," "move immediately if you feel nauseous," or "hydrate at regular intervals" can help prevent overexertion.

Especially when accompanied by children, it is necessary to clarify roles, such as "who will supervise," "within what range can they play," "will an adult always be near the water," and "conduct headcount checks at set intervals, e.g., every 30 minutes." Since children can become engrossed in play and may not easily recognize heat or illness, it is crucial for adults to proactively encourage breaks and hydration.

During summer leisure, people tend to push themselves with thoughts like "since we came all this way" or "just a little longer," but heatstroke and accidents can become serious in a short period. To enjoy safely, it is important to set rules in advance and share them with all companions.

If You Don't Have an Appetite in the Morning, Try a Jelly Drink

Going on summer outdoor leisure without eating breakfast increases the risk of heatstroke. On the day of summer leisure, many people leave early in the morning and may eat during transit. Some might also skip breakfast due to a lack of appetite caused by the heat. However, during sleep, not only do we sweat, but we also experience "insensible perspiration," where water is naturally lost through breathing and the skin. Therefore, upon waking, the body is already in a state of mild dehydration. Skipping breakfast on top of this means starting the day with a deficiency in essential nutrients like water, electrolytes, carbohydrates, vitamins, and proteins needed for normal bodily functions.

During summer leisure, due to heavy sweating caused by the heat, not only water but also electrolytes like sodium are lost. Electrolytes are crucial for maintaining the body's water balance and the function of nerves and muscles. A deficiency can lead to symptoms such as dizziness, lightheadedness, leg cramps, and fatigue.

Furthermore, carbohydrates are the primary energy source for the brain and muscles. A deficiency can lead to reduced concentration and impaired judgment, potentially resulting in falls or water-related accidents.

An ideal breakfast includes staples like rice or bread, combined with items such as miso soup, soup, eggs, fish, meat, natto, yogurt, and fruit, to provide a balanced intake of water, electrolytes, carbohydrates, and protein. Miso soup and other soups are suitable for summer breakfasts as they provide both water and salt.

Proteins and amino acids abundant in fish and seafood are important for maintaining muscles and overall physical condition for active movement. Amino acids are involved in maintaining muscle and bodily functions and are also being studied for their role in aiding the absorption of water and electrolytes, making them beneficial for maintaining condition in hot environments.

B vitamins found in eggs, natto, and pork help convert carbohydrates, fats, and proteins into energy, supporting energy metabolism during the summer when it is easily depleted.

Taurine, found in seafood, is another component to consider for fatigue prevention.

Citric acid is also a nutrient to incorporate for fatigue prevention during hot leisure days. It is found in lemons, oranges, grapefruits, and pickled plums.

On the other hand, if you don't have time for breakfast or lack appetite due to the heat, using jelly drinks is recommended. Jelly drinks containing water, carbohydrates, and electrolytes are easy to consume even when you don't feel like eating in the morning and can be conveniently replenished during transit or breaks. Opting for jelly drinks that also contain amino acids, B vitamins, and citric acid is advisable.

"Accidentally skipping breakfast" can lead to dehydration and reduced physical performance, posing a significant risk. Therefore, it is recommended to pack jelly drinks in advance.

Prepare to Cool Down from the Inside with Ice Slurry and Chilled Jelly

In recent years, attention has shifted not only to cooling the body from the outside but also to cooling it from the inside as a heatstroke prevention measure. One such method is the use of ice slurry and frozen jelly drinks.

Ice slurry is a sherbet-like beverage mixed with liquid and fine ice particles. It can be purchased at supermarkets and convenience stores, and when frozen at home, it reaches a soft consistency that can be consumed about 15-20 minutes after being taken out of the freezer.

As the fine ice particles melt slowly inside the body, they absorb deep body heat, helping to suppress the rise in core body temperature while replenishing fluids. This measure can be easily incorporated during outdoor leisure activities, such as before departure, during transit, between activities, or during breaks after prolonged sun exposure.

Chilled jelly drinks and frozen beverages are easy to consume even when appetite is low due to heat and can be used to replenish water, carbohydrates, and electrolytes when feeling fatigued from the heat.

Hydration Principle: "Before You Feel Thirsty," Conscious of Electrolytes and Carbohydrates, Not Just Water

Frequent hydration is essential during summer outdoor leisure. However, the key is to drink small amounts frequently *before* you feel thirsty, rather than waiting until you are thirsty.

By the time you feel thirsty, your body may already be experiencing a deficit in water. Especially during outdoor leisure, it is easy to delay hydration while engrossed in activities, leading to unnoticed dehydration.

It is important to replenish electrolytes such as sodium and potassium along with water, rather than just drinking large amounts of water. Sweat contains not only water but also salt, so continuously drinking only water can disrupt the body's electrolyte balance and lead to poor physical condition. Furthermore, carbohydrates play a crucial role in heatstroke prevention. Carbohydrates are an energy source for the brain and muscles and are necessary to support concentration, judgment, and physical movement during activities.

For prolonged outdoor leisure or situations with heavy sweating, be sure to bring sports drinks, jelly drinks, or oral rehydration solutions and consume them according to the situation.

First Aid to Know

Heatstroke can be prevented from becoming severe if appropriate measures are taken in the early stages. However, delayed response can be life-threatening. Initial symptoms include dizziness, lightheadedness, headache, nausea, fatigue, heavy sweating, calf cramps, flushed face, feeling dazed, or slow reactions. If such symptoms appear, stop the activity immediately and do not push yourself.

The basic first aid measures are to move to a cool place, loosen clothing, cool the body, and replenish fluids and electrolytes. Cooling areas where large blood vessels are close to the surface, such as the neck, armpits, and groin, is particularly effective for lowering body temperature. Use cold packs, ice packs, cold water bottles, or wet towels. If the person can drink independently, replenish fluids and electrolytes with oral rehydration solutions. If unable to drink a large amount at once, it is important to consume small amounts frequently.

However, if the person's response to calls is abnormal, consciousness is unclear, they cannot walk straight, cannot drink fluids independently, are repeatedly vomiting, have seizures, their body is abnormally hot, or they do not recover despite first aid, they may have already developed a severe condition. In such cases, forcing fluids can lead to aspiration, so it is necessary to seek immediate medical attention or call an ambulance. Heatstroke can rapidly worsen in a short period. Do not self-diagnose with "I'll be fine after a rest"; if you notice any signs of abnormality, provide rest immediately and connect with medical services or emergency consultation.

Don't Let Your Guard Down After Returning Home. Beware of "Delayed Heatstroke"

Even if there are no problems during the day while playing, physical discomfort may appear after returning home or at night. This is because fatigue from the heat, dehydration, lack of fluids and electrolytes, and disruption of thermoregulation that were not noticed during the day manifest with a delay. Symptoms can include headache, nausea, fatigue, fever, loss of appetite, feeling dazed, or excessive sleepiness, sometimes referred to as "delayed heatstroke." Dehydration caused by bathing or drinking alcohol after leisure can also trigger this.

Children, in particular, may have difficulty articulating changes in their condition. Therefore, after returning home, it is important for guardians to carefully observe for changes such as "less energetic than usual," "taking a nap when they normally wouldn't," "flushed face," "lack of appetite," "not wanting to drink," or "dark urine color."

Summer outdoor leisure can create precious memories with family and friends, but it also carries risks such as heatstroke, dehydration, injuries, and water-related accidents. Especially with the increasing number of extremely hot days in recent years, extra caution is needed for outdoor activities. To enjoy summer leisure with peace of mind, be conscious of a series of measures from pre-trip preparations and frequent checks during activities to post-return health checks.

FACT BOX

  • Source: PR TIMES
  • Category: Survey結果