What does a long-haul flight actually do to your body?  : Science alert

What does a long-haul flight actually do to your body? : Science alert

What does a long-haul flight actually do to your body?  : Science alert

If crowded airports are a sign, people are dying to get back in the air. And if you fly long-haul, you might have an even longer option in a few years.

Qantas has announced it will be carrying passengers on non-stop flights from Australia’s east coast to London from the end of 2025, which would see you in the air for more than 19 hours at a time. That compares to current flights, which last the better part of 24 hours but are broken up into shorter segments.

So what happens to your body during one of those longer flights? Is it different than when you fly long-haul now?

1. You can become dehydrated

Dehydration is common on long-haul flights. It may explain why your throat, nose and skin can feel dry on an airplane. The longer the flight, the greater the risk of dehydration.

That’s because of the low humidity in the cabin compared to what you’d expect on the ground. This is mainly because a lot of the air circulating through the cabin is drawn in from the outside and there isn’t much moisture in the air at high altitudes.

You also risk dehydration if you don’t drink enough water or drink too much alcohol (alcohol is a diuretic, leading to increased fluid loss).

So drink water before boarding the plane. During the flight, you also need to drink more water than usual.

2. The cabin can wreak havoc on your ears, sinuses, gut, and sleep

When the cabin pressure changes, the gas in our body reacts accordingly. It expands as the plane climbs and the pressure decreases, and the opposite happens when we descend. This can lead to common problems such as

  • Earache – when air pressure is different on either side of your eardrum, putting pressure on the eardrum
  • Headaches – can be caused by the expansion of air trapped in the sinuses
  • Gut problems – just accept that you will fart more.

You may also feel more sleepy than usual. This is because the body cannot absorb as much oxygen from the cabin air at altitude as it can on the ground. Slowing down is the body’s way of protecting itself and it can make you feel drowsy.

The good news is that most of these problems are not necessarily more pronounced on longer flights. They are mainly a problem when the plane climbs and descends.

3. You could develop blood clots

Blood clots associated with prolonged immobility are usually a major concern for passengers. These include clots that form in the leg (deep vein thrombosis, or DVT) that can travel to the lungs (where it’s called a pulmonary embolism).

If you are not moving on an airplane and the more of the following risk factors you have, the more likely it is that you will develop blood clots:

  • older age
  • obesity
  • History or a family history of blood clots
  • certain types of clotting disorders
  • Cancer
  • recent immobilization or surgery
  • pregnancy or recent birth
  • Hormone replacement therapy or oral contraceptives.

According to a 2022 review that combined data from 18 studies, the longer you travel, the greater your risk of blood clots. The authors calculated a 26 percent higher risk for every two hours of air travel, starting after four hours.

So what about the risk of blood clots on those longer flights? We won’t know for sure until we start studying passengers on them.

Until that evidence is available, the current advice still applies. Keep moving, stay hydrated and limit alcohol consumption.

There is also evidence of wearing compression stockings to prevent blood clots. These stockings are designed to increase blood flow in the legs and help blood flow back to the heart. This would normally happen through muscle contractions from exercise or walking.

A 2021 cochrane The review combined the results of nine studies involving 2,637 participants who were randomized to wear compression stockings (or not) on flights longer than five hours.

No participant developed symptomatic DVTs. But there was evidence that people who wore the stockings significantly reduced their chance of developing symptomless clots, and we know that any clot can potentially grow, move and subsequently cause symptoms.

So if you’re concerned about your risk of developing blood clots, see your GP before you fly.

If you develop a blood clot, you usually don’t know about it until after the flight, as the clot takes time to form and travel.

So watch out for post-flight symptoms – pain and swelling in one leg (often just one), chest pain, coughing and shortness of breath. And if you do, seek emergency medical care.

4. Then there’s jet lag, radiation, COVID

Then there’s jet lag, which few of us are unfamiliar with. This is a discrepancy between what your body thinks it can tell you and what the clock tells you when you cross time zones.

Longer flights mean you’re more likely (but not always) to cross more time zones. Jet lag usually becomes more of a problem when you cross three or more, especially when traveling east.

And anyone who takes long-haul flights very often can assume that the longer you are in the air, the higher the exposure to cosmic radiation.

As the name suggests, it is radiation from space that can increase the risk of cancer and reproductive problems. We do not know what level of exposure is safe.

However, this is unlikely to be a problem unless you fly frequently. If you are pregnant or have any other concerns, speak to your GP before you fly.

And don’t forget COVID. Take the usual precautions – wash your hands regularly, wear a mask and don’t fly if you feel unwell.

In short

Research into how the body responds to these longer, non-stop flights between Australia and Europe is still in its infancy. Teams in Australia are looking at this now.

If you’re taking a regular long-haul flight by then, the advice is relatively straightforward.

Follow airline advice and, if necessary, consult your GP before travelling. During the flight, you should make an extra effort to move about in the cabin, drink water, wear a mask and practice good hand hygiene.

If you have any worrying symptoms after your flight, seek immediate medical attention as blood clots can take hours or even days to form, grow and move through your veins.The conversation

Tony Schiemer, commercial pilot | Aerospace Medicine Specialist | Clinical Lecturer, University of Adelaide

This article was republished by The Conversation under a Creative Commons license. Read the original article.

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