They make a habit of napping
It’s been shown that lack of sleep causes weight gain, leads to a compromised immune system and increases the production of cortisol, a hormone that triggers stress. But Sarnoff Mednick, professor emeritus of psychology at the University of Southern California, doesn’t worry about such things. As profiled by Gene Stone in his book The Secrets of People Who Never Get Sick, Mednick would take an afternoon nap for most of his adult life and never suffered from colds or flu. The fact is, until about the 13th century and the invention of mechanical clocks, humans napped daily. The best time for a short snooze: Between the hours of one and three in the afternoon. These common household items could be the reason you’re always getting sick.
They skip the nightcap
Although you may feel as though you fall into a deep slumber after a night of drinking, alcohol actually disrupts your sleep cycle and compromises the quality of your sleep. Sleep is so wonderfully restorative to your immune system; cutting back on drinking will help your body protect against harmful germs you might be encountering.