As Cold Waves Continue In India, How Does Extreme Cold Weather Affect Your Body?

At least 22 cold-related deaths have been reported so far in UP, with nearby Delhi experiencing temperatures of 2°C.

Temperatures dipped to 2°C in the capital in January 2023.

(Illustration: Vibhushita Singh/ The Quint)

On 5 January, 22 people reportedly died from heart attacks caused by extreme cold in Kanpur, Uttar Pradesh. In 2020 alone, the total cold-related deaths in India stood at 776.

The Indian Met Department has predicted cold wave and severe cold wave conditions in many parts of North India.

How does an extreme cold wave affect our body? What happens if you're exposed to sub-zero temperatures? What happens to someone if they spend a night in the cold with no protection from the winds of winter?

Here's everything you need to know about how extreme cold affects the human body.

What Happens to the Body During a Cold Wave?

Like we've mentioned in the past, humans are endotherms, which means our internal temperatures stay constant despite changes in external temperatures.

This internal temperature hovers around 36.8°C to 37.4°C, and in response to external temperatures rising or falling, our body compensates by either warming itself up (by shivering) or cooling itself off (by sweating). This is called homeostasis.

In the simplest terms, as the outside temperature falls, your internal temperature rises, and as outside temperature rises, your body tries to dissipate heat by sweating to cool off. This process is called thermoregulation.

Your body can only warm or cool itself to a certain extent, and when it can no longer keep up with the temperature extremes, it starts to suffer from some very concerning effects. In the case of extreme summer or heatwaves, you face heat exhaustion, fatigue, dehydration, and possibly heat stroke, and in the case of extreme winter or cold waves, you can suffer from hypothermia, frostbite, and even heart attacks.

"We see people from the middle and upper-middle class experiencing some of these problems, but the worst affected are the poor, who often have to deal with hypothermia."

Dr. Sumit Ray, Critical Care Specialist

According to Dr Sumit Ray, who's worked as a critical care specialist for over 25 years, people with heart problems, older people, and infants are likely to experience increased heart problems, breathing issues, and other issues from cold weather.

The Road to Hypothermia

The National Library of Medicine defines hypothermia as "an involuntary drop in internal body temperature below 35°C." It isn't confined to just colder regions and can be caused by a range of reasons including illnesses that affect your body's ability to effectively retain or dissipate heat.

Now, as the external temperature falls, your internal temperature rises to maintain homeostasis. When your body can no longer generate more heat than it dissipates, your internal temperature starts to fall.

• When your internal temperature drops to below 35°C, you'll start experiencing the symptoms of mild hypothermia. From 35°C to 32°C, you'll suffer from impaired judgement, amnesia, and hyperemia.

• When your blood flow changes to different parts of your body, it's called hyperemia. Active hyperemia happens for many reasons including exercise, fever, cold, or digestion.

• In this case, hyperemia occurs when blood from your extremities flows to your core and your vital organs. Your body begins to focus its efforts on keeping your core and your vital organs warm and in a state of homeostasis.

• This leads to your liver, spleen, heart, and lungs getting more circulation, while your extremities — your fingers, toes, nose, and earlobes, receive less circulation, and become colder.

• In an effort to stay warm, you'll also start to shiver and undergo vasoconstriction, which is science talk for your blood vessels contracting and increasing your blood pressure and circulation. Both of these happen as your body struggles to warm itself. This increased blood pressure can also lead to hypertension in some individuals.

• As your core temperature slowly falls, you'll also have trouble speaking and even thinking, because you'll start experiencing dysarthria, which is when you're unable to speak because of brain damage from extreme cold. You'll also begin to lose your motor skills at this point.

• As you approach moderate hypothermia, your body tries everything to warm you up, including putting you into a state of tachycardia, which is a heartbeat above 100 beats per minute.

From Mild to Moderate Hypothermia

As your internal temperature falls below 32°C, you begin to experience moderate hypothermia. This is when your impaired judgement escalates to confusion, agitation, lethargy, and even hallucinations.

People also sometimes begin to undress themselves in a symptom called paradoxical undressing. This is believed to be caused by your hypothalamus malfunctioning from the cold, causing even more confusion and disorientation.

Another theory says that paradoxical undressing occurs when your blood vessels suddenly get exhausted from the increased pumping, and you suddenly experience a large spike in heat all over your body. Either way, in many hypothermia deaths, victims are found in a state of undress, brought on by paradoxical undressing.

• Like paradoxical undressing, which seems counter-intuitive to survival, as you get colder, your breathing slows, and your blood pressure drops (hypotension).

• Your enzyme activity slows down and you're likely to experience nausea as the insides of your stomach suffer from gastric erosion, i.e., the destruction of your stomach's lining because of excess acid. Meanwhile, the slowing of blood flow also leads to localised edemas, which are swellings caused by fluid retention.

• Your heart, which was pumping blood at an increased rate, now experiences hypotension, which is a slowed pumping of blood.

• Your body, which was shivering to keep itself warm up to this point, will now stop shivering and experience muscle rigidity.

• All of these combine to drop your body's temperature even more. Failing to intervene at this point, whether that's by putting on warm, loose clothes and/or sitting indoors by a fire, can quickly turn fatal, since your core temperature is dropping fast.

Severe Hypothermia, Frostbite, and Death

As your core temperature drops, your hypothermia progresses from mild to moderate, and eventually to severe hypothermia, i.e., an internal temperature that's below 28°C. When your internal temperature falls below 28°C, you'll be dangerously close to death from hypothermia.

At this point, you'll begin to experience delirium, hallucinations, and potentially enter a comatose state. Simultaneously, your heart rate starts to fluctuate and drops to below 60 beats per minute, as you begin to suffer brachycardia.

If your internal temperature falls below 20°C your heart could simply stop beating, because of a condition called asystole.

Your blood's ability to clot also takes a hit, which means any wounds or cuts that you have, will be bleeding profusely. Your kidney function approaches renal failure levels as it gets colder.

Fighting this alone becomes very difficult, since your reflexes have now stopped working because of a condition called areflexia, and your pupils are fully dilated and non-reactive. Your brain, if it's survived the delirium and hallucinations, now enters a state of stupor.

Even your digestive system isn't safe since your stomach's lining starts to literally melt away because of something called gastric erosion.

In extreme cases, when parts of your body, usually your extremities, fall below -2°C, you'll start freezing on a cellular level, and the formation of ice crystals on your cells leads to cell destruction, dysfunction, and cell death(necrosis). This is called frostbite.

For context, an external temperature of 0°C is enough to trigger death from cold exposure, and in some cases, even temperatures as high as 15°C can lead to frostbite.

Other Cold-Related Disorders

Like we mentioned, exposure to temperatures as low as 15°C can lead to one of two conditions – chilblains and/or trench foot. Chilblains is the formation of blisters under your skin from being exposed to temperatures of 0 to 15°C. In the worst-case scenario chilblains can cause painful blisters under your skin.

Trench foot, on the other hand, occurs from prolonged exposure to cold and wet conditions. If your leg has been wet and exposed to temperatures in the 0-15°C range, you run the risk of trench foot. Similar to chilblains, it causes a painful tingling sensation and if left untreated, it can lead to gangrene and blisters.

How to Stay Safe?

According to Dr. Sumit Ray, "For mild hypothermia, warming will include making the person put on blankets and providing external heating. If they can drink fluids, they should drink warm fluids. All of this should ideally be in a room without any warm air."

Dr. Ray adds that in case someone is brought to the hospital for a more moderate case of hypothermia doctors will use warming blankets, and ensure ingestion of warming fluids. In cases of severe hypothermia, he adds, "we use a special machine that warms the person's blood, almost like a dialysis machine, and recirculates it through their body."

He adds that staying safe would include drinking warm fluids, using a coil-based heater, and wearing multiple layers of loose clothes to stay warm.

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