...perceived age was significantly associated with survival, even after adjustment for chronological age, sex, and rearing environment. Perceived age was still significantly associated with survival after further adjustment for physical and cognitive functioning. The likelihood that the older looking twin of the pair died first increased with increasing discordance in perceived age within the twin pair—that is, the bigger the difference in perceived age within the pair, the more likely that the older looking twin died first.
The photo embedded above is a computer-generated composite of 10 pairs of twins. "Left hand image represents twins who looked younger for their age (average perceived age 64, range 57-69) than those represented by right hand image (average perceived age 74, range 70-78)."
There are a variety of factors which may be instrumental in this relationship, including smoking status, body mass index, and sun exposure. These and other relevant factors are discussed at the link. The study was conducted in twins to minimize variables, but the conclusions may extend beyond twins to the general population.
Link to fulltext BMJ article, via the BBC.