British Psychological Society
Researchers rated the "smile intensity" of 230 baseball professional baseball players. Focusing on the 150 players who'd died by the time of the study and controlling for extraneous factors such as BMI and marital status, the researchers found that those who were flashing a genuine 'Duchenne Smile' were half as likely to die in any given year compared with non-smilers. Indeed, the average life-span of the 63 deceased non-smilers was 72.9 years compared with 75 years for the 64 partial smilers and 79.9 years for the 23 Duchenne smilers.
The question, of course, is does smiling make you healthier, being healthier make you smile more, or perhaps most likely, a smile is a sign of an upbeat personality, which has been linked to longevity in numerous studies -- check out this cool study of nuns in particular.
