Decreased sleep quality linked to premature skin aging

Here is an article discussing research showing that decreased sleep quality may increase risk of premature aging and decrease the skin's ability to recover from sun exposure. Sleep quality was assessed with a subjective sleep questionnaire, and it's not clear if the results were linked to decrease total sleep amount and / or reduced sleep quality. Also, I have to assume, but do not know for a fact, that the researchers controlled for other factors that affect skin like tobacco use.