According to new research, cigarette smoke affects the expression of genes related to your circadian rhythm, which is largely responsible for regulating your sleep—numero uno for health and beauty. In studies of mice and humans, smokers (and patients with chronic obstructive pulmonary disease (COPD)) showed a reduction in the level of the aptly named clock protein, leading to disruptions of the sleep cycle. One more reason to make quitting a goal for 2014.

MORE: Take the Sleep Quality Quiz and See If You’re Getting the ZZZ’s You Need