Researchers from Victoria University (Australia) tracked 3,000 elderly men and women for 15 years, and reported in 2005 that married men lived, on average, 11 months longer than their single counterparts. Marriage, however, was found to have little effect the lifespan of married women.  A previous study, by a team at University of Victoria (Canada), that followed 9,775 men and women, found that men and women report a decrease in physical or mental health when they ended a marriage or stopped living with their partner.

Some scientists have put forth a theory called the "marriage protection hypothesis," suggesting that married couples improve their health by providing each other with social and financial support, and by monitoring each other's health behaviors. 

"If thou wouldst marry wisely, marry thine equal." ~ Ovid