The heatwave has disrupted travel, delivery services and nearly every aspect of our daily lives, but why are some people affected more than others by the heat?  And what are the all-important strategies for coping in a heatwave?

On Tuesday, 19th July 2022, the temperature exceeded 40°C (40.3 °C) for the first time in England, the previous highest being 38.7 in Cambridge on 25th July 2019.  The heatwave headed north, reaching 34.8 °C in Scotland, compared with the last Scottish record of 32.9°C in 2003.

Buildings and infrastructure in the UK are not designed to cope with such heat.  The heatwave caused extensive travel disruption by rail, plane, and road – delivering goods and services.  Accidents occurred on melted roads; airport runways and bridges were unstable; and countless wildfires raged, overwhelming fire brigade resources.

The heatwave in the UK and western Europe is very overwhelming. But why are WE personally not coping with it?

The human body is designed to function optimally at a temperature of 37°C.  Heat-related illness occurs when our body cannot handle environmental temperature fluctuations.  Mortality increases by an average of 2% for every 1°C rise in temperature.  The heat threshold is higher in people living closer to the equator since they are more adapted to a hot climate.

People living in the UK and western Europe have a general tendency for chronic dehydration (a risk factor for heat-related illness) due to inadequate water intake and the consumption of excessive fluids that cause dehydration, such as commercial fruit juices, alcohol, and caffeine.  In contrast, the Mediterranean culture encourages hydration by providing a glass of water with every cup of tea, coffee, or glass of wine.

How does a heatwave occur?

The year 2022 has been a particularly arid one (low rainfall). The sun’s rays fall on bare land to heat the air and escalate the atmospheric temperature rather than be absorbed by vegetation and grass.  There is also an accumulation of greenhouse gas in the atmosphere because carbon dioxide emissions increased in 2021 by 6% to 36.3 billion tons, the highest ever level.

A heatwave is a significant medical concern: 2,244 over-65s died in the UK in August 2020, when the temperature exceeded 38 in some parts of the UK for six consecutive days.  And more than 70,000 died in Europe during the 2003 heatwave.  Extreme temperature kills 5 million people worldwide every year.

(Unfortunately, as people seek cooler areas, such as rivers, lakes and the sea, this has caused an increase in the number of people drowning.)

Heat-related illnesses and deaths are generally preventable.

Who is at risk in a heatwave?

Heat-related illness can affect anyone, but the risk is greater for older adults, overweight or obese (overweight or obese bodies retain more heat), babies and young children (under 4 years), and people with pre-existing chronic health conditions.

The risk of heat-related illness is higher in people who perform vigorous physical activity outdoors, mainly those who work in construction and agriculture.

Cardiovascular stress during a heatwave wave is often deadly!

Extreme heat increases hospital admissions and can be fatal.  It can result in a heat-related illness, such as heat exhaustion or heat stroke.  It can also exacerbate a pre-existing cardiovascular, respiratory, or chronic kidney disease or dementia.  People living with Asthma are at high risk, but cardiovascular diseases like hypertension, heart disease and stroke are the most deadly, accounting for 43% of all deaths.

It is well known that heat and humidity trigger acute asthma attacks because heat makes air pollution worse, negatively impacting your lungs.  Ozone pollution, often called smog, is common during the summer months.  Heat causes ozone gases to react and aggressively attack lung tissue.

Heatwaves overload already-failing hearts, which are unable to meet the increasing demands!

With a rise in core body temperature, the heat regulation centre in the brain (hypothalamus) shunts more blood to the skin to increase sweating.  Evaporation of sweat helps the body to release excess heat into the environment.  However, the increased blood flow to the skin challenges the cardiovascular system, putting more pressure on the heart to pump harder and faster.  This often compromises the circulation in patients with pre-existing heart diseases.

Heat also stresses the cardiovascular system due to the loss of salt and water in sweat, causing blood to thicken, which in turn increases the risk of thrombosis (clot formation) in the heart and brain circulation, often resulting in a heart attack or stroke.

Very few heat-related deaths in the UK are caused by hyperthermia. However, some patients cannot sweat because they have diabetic autonomic neuropathy or are taking anticholinergic drugs.  Some patients also take medicines, such as barbiturates or phenothiazines, which depress the brain’s response to changes in body temperature.  Drinking alcohol in the heat is not safe either, as alcohol depresses the central nervous system and causes diuresis, fluid loss and dehydration.

Why are older people vulnerable?

Older people are weak in protecting themselves from soaring temperatures by seeking shade or air-conditioned environments.  These ‘cooling strategies’ are sought out less often than in the younger generations.

Older people typically have poor water balance and may become dehydrated and slip into renal failure, with a poor effect on the cardiovascular system.  They are also likely to be on medications that may interfere with the normal sweating process and other systems that regulate body temperature.  They are more likely to live alone and have less social support.

Dehydration is a common challenge in elderly adults with dementia because they often forget to drink and don’t have the support to keep their fluid levels up when temperatures soar.  In addition, a fall outside during a heatwave could have a devastating effect.

The effect of pharmaceutical drugs

Medications may depress the brain reflex, suppress the circulatory system response to heat, or deplete the body fluids and cause dehydration, a major risk factor for heat-related conditions.

Beta-blockers (heart pills) reduce the ability of the heart and lungs to respond to increasing demand in heat-related stress.  Diuretics (water pills) act on the kidneys and encourage fluid loss.  This can quickly lead to dehydration in hot weather.  Opioids and sedatives can reduce the person’s awareness of physical discomfort, which means that the symptoms of heat stress may be ignored.

Everyone should, of course, stay on their medication and seek their GP’s advice if necessary.

Tips to stay safe during the heatwave

Stay hydrated: continue to take fluids, aiming for 2 to 3 litres per day, with older adults needing more.  Clear water is the best hydration fluid because juices and fizzy drinks cause dehydration – the body gets rid of excess sugar by producing more urine.  Sip water regularly and avoid drinking a large volume at once, pushing your body to produce the diuretic hormone to get rid of excess water.  You should also eat vegetables and fruits high in water, such as watermelon, berries, cucumber, and celery.

Home is where you keep cool: keep windows closed and blinds down during the day to stop outdoor heat and reopen them when it gets cooler in the evening.  Use fans, coolers or air-conditioning to keep the indoor temperature down.  If you have to work outside, take frequent breaks, and have a cool bath or shower when it’s too hot.  Reduce your travel to a minimum (only when necessary), and of course, do not leave children or pets in a car, as this can result in disaster.

Alcohol and caffeine should be limited: these are diuretics which cause dehydration – contrary to the behaviour of many people who go out in summer to enjoy drinking more alcohol.  (Again, the Mediterranean custom of providing water with every caffeinated or alcoholic drink can overcome much of this danger.)

Dine intelligently: reduce your oven and stove use, as these generate a lot of heat.  A slow cooker or air fryer are better options in the hot summer.  In this case, it would be prudent to follow the old African cultures and enjoy plenty of raw fruits and vegetables, mainly those high in water like watermelon (which is what nature provides at this time of the year) and eat plenty of salads and light-cooked meals.  And leave your steak (or similar) serious cooking for the cold winter.

Elderly adults may not feel overheated but encourage them to stay indoors between 11 am and 4 pm, wear a hat outdoors, avoid heavy synthetic fabrics, and wear light cotton to keep cool.  Older people are sensitive to sudden changes in light, which may result in a fall when outdoors.

People are also advised not to have barbecues or bonfires and to be careful when disposing of cigarettes due to the fire risk.

Heat stroke and heat exhaustion

Your body temperature stays between 36.52°C and 37.5°C.  When it rises above 37.5°C, you have a fever, also called pyrexia.  Hyperpyrexia is the terminology used for a temperature above 41.5°C, usually due to an underlying cause such as an infection.  However, an increase in body temperature due to a high ambient temperature is known as hyperthermia.

Heat exhaustion is characterised by excessive sweating, dehydration (salt and water loss), and a temperature rising to over 38°C.  The symptoms of dehydration are fatigue, feeling thirsty, dizzy, giddy, or lightheaded, muscle cramps, reduced urine output to a small volume of dark yellow, strong-smelling urine, low blood pressure, and fast heart rate.

Heatstroke, on the other hand, is a serious medical emergency with the body temperature rising to a dangerous level above 40°C.  This results in severe dehydration, headache, extreme confusion, loss of consciousness, extreme shallow and fast breathing, seizures, and can progress to multiple organ damage and death.

If you experience any heat-related illness, check your temperature: above 38 indicates heat exhaustion, whilst above 40 is a sign of heat stroke.  Find a cooler location, if possible, a shady area or indoors, drink water or any other fluids, and seek medical help immediately.

While waiting for the emergency services, remove any tight or extra clothing, sponge the body with tepid water or have a cool bath, replace fluids through drinking, and give simple analgesia to reduce the high temperature.

You must be extra careful if you move from a cold to a hot environment, for example, by having a winter holiday in a hot place, as your body may not adapt quickly due to a slow thermoregulatory centre.

Do remember my simple S.H.A.D.E. mantra for dealing with the heatwave – Stay hydrated, Home is best, Alcohol and caffeine are best avoided, Dine without heating the whole house, and the Elderly need particular care.

As always, my friends, if you have any questions about this unprecedented physical challenge or would like to share your heatwave experiences, I would be delighted to hear from you.  And your contribution may help someone else stay safe through the long, hot summer of 2022.



The main causes of UK heatwave deaths 2022

Heat-related mortality: a review and exploration of heterogeneity

Do you have heat stroke or heat exhaustion? Learn the signs

What is hyperpyrexia?