Exposure to smoke can lead to shrinkage—in your brain. An earlier study found that people who lit up only on the weekends damaged their memory just as much as people who puffed daily, and now a new study finds that you don't have to have a butt habit at all to have your recall hurt by cigarette smoke. 

Researchers wrote about their new study in the journal Addiction after giving memory tests to three groups: non-smokers not exposed to second-hand smoke, non-smokers who were exposed to second-hand smoke (25 hours a week for 4 and a half years), and current smokers. 

The findings were alarming for your memory’s sake:

  • Current smokers forgot 30 percent more than those who were not exposed to second-hand smoking.
  • Both groups of non-smokers outperformed the smokers, but…
  • Non-smokers who had been exposed to second-hand smoke forgot almost 20 percent more than those not exposed to second-hand smoking.

Even if you don't smoke, you're still killing your memory by breathing in cigar smoke from, say, the other guys at your weekly poker games, or from your chain-smoking girlfriend. Try to cut down on your exposure to smoke wherever you can, whether it means steering clear of the smokers outside the bar or telling your pals who smoke that they can't light up in your car.