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Sleeping In Cars Is Bad for Your Legs

Everyone with a history of deep vein thrombosis knows the plane drill. Flying is hard on people who are at risk of getting blood clots in their legs.

And we now have real-world proof that sleeping in cars is a bad idea, too. For all of us. 

In April 2017, after the Kumamoto earthquake, thousands of Japanese were afraid to return to their homes because a large number of aftershocks were still rumbling through the area. Shelters were crowded, so many people opted to sleep in their cars.

That was the beginning of KEEP—the Kumamoto Earthquake Thrombosis and Embolism Protection project.

The project came about because, after the Kumamoto earthquake, an unusually high number of people developed clots in their legs. For some, the clots broke loose and went to their lungs as venous thromboembolism (VTE).

The KEEP team found 51 patients who were admitted to hospitals for troublesome clots and asked them what they had done in the days beforehand. An astounding 42 patients (82%) in the group had spent a night in their car.

More surprising, and definitely more worrisome, 35 of these people developed a VTE.

What is most compelling about this is the clear link between inactivity and VTEs. Nine of the people in the study who showed up at Kumamoto area hospitals reported that they had not slept in their cars. Three of them (33%) developed VTEs.

But among the 42 people who did report they had slept in their cars, 35 of them (83%) developed VTEs.

This is not to say that sleeping in cars will definitely lead to clots in your legs or a VTE. But if you have a risk factor, you should be concerned. Ditto flying.

"This is a dramatic example of the risks inherent in spending prolonged periods immobilized in a cramped position," commented Stanley Nattel, MD, Editor-in-Chief of the Canadian Journal of Cardiology, which published the results.

We'd all prefer to avoid earthquakes, floods, hurricanes and natural disasters, of course. But sometimes the only way to get where we want to go in a reasonable amount of time is to fly.

We looked at recommendations from the Centers for Disease Control in the US and the National Health Service in Britain. It turns out that a lot of us should be aware of the risk of blood clots when we are forced to stay fairly inactive and cooped up in a small space.

Here's what doctors say:

You might be at risk even if you've never had a clot before. You are at higher risk if you smoke, have cancer, have had recent surgery in the pelvic area or legs, have varicose veins, are obese, or have any history of heart disease.

For women, being pregnant, using hormone replacement therapy, and using estrogen-containing birth control also increase your risk.

To lower your risk of a clot, this is what the doctors advise:

Dress comfortably in loose clothing (there will be an additional reason for this). Avoid alcohol or sleeping pills (yeah, we know), and drink plenty of water.

Also, consider compression stockings if your legs tend to swell or feel extra tired after inactivity and travel. NHS recommends a 14-17 mmHg pressure at the ankle. That's a low to moderate amount of compression. NHS also notes that these stockings need to be measured and fitted correctly or you could increase your risk of a deep vein thrombosis.

Your second line of defense is on the plane. Or in the car, if you really must sleep there.

When possible, stand for a while once per hour, walk around a bit if you can. On a plane, an aisle seat is best if you can snag one. But no matter what, do some leg exercises. The simplest one is ankle circles. Also, stretch your legs and flex your ankles (pull them toward you).

The reason for comfy clothes, and pants, in particular, is that you might want to do this one more exercise sometimes recommended by the airlines. Grab one knee with both hands and pull it up toward your chest. Hold for a count of 15. Repeat 10 times. Then do the other leg.

That's not something we recommend in a dress or a kilt. Bon voyage!

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