Smoking Plus Heavy Drinking Speed Cognitive Decline, Study Finds

Taken individually, it's no secret that smoking and drinking too much alcohol are not good for health. And now, a new study shows that doing the two together could spell special trouble for your brain.

The findings, published in the British Journal of Psychiatry, show that smokers who heavily drink have a faster cognitive decline than people who don't smoke and drink alcohol only moderately.

"Current advice is that smokers should stop or cut down, and people should avoid heavy alcohol drinking. Our study suggests that people should also be advised not to combine these two unhealthy behaviors -- particularly from mid-life onwards," study researcher Dr. Gareth Hagger-Johnson, of University College London, said in a statement.

For the study, researchers looked at the smoking and drinking habits, as well as cognitive functioning, of 4,635 men and 1,838 women between ages 45 and 69 who were part of the Whitehall II cohort study. They were followed over a 10-year period; their cognitive functioning was analyzed three times during that time.

Researchers found links between decreased cognitive functioning and people who smoked and drank heavily. Specifically, people who were heavy drinkers and cigarette smokers had a 36 percent faster rate of cognitive decline, compared with people who were just moderate drinkers and didn't smoke.

And "when we looked at people who were heavy-drinking smokers, we found that for every 10 years that they aged their brains aged the equivalent of 12 years," Hagger-Johnson noted in the statement.

For the study, non-drinkers were defined as drinking no alcohol during the week, while moderate drinkers were defined as drinking "1-14 units a week for women or 1–21 units per week for men." Heavy drinkers were defined as drinking more than 14 units a week for women, and more than 21 units a week for men. The United Kingdom looks at alcohol content in beverages in terms of units; according to the UK's NHS, women shouldn't drink any more than two to three units of alcohol in a day, while men shouldn't drink more than three to four units of alcohol in a day. Hagger-Johnson explained that one unit of alcohol is about half of a standard drink in the United States.

In the United States, the Centers for Disease Control and Prevention considers moderate drinking as one drink a day for women, and two drinks a day for men.