Between 2001 and 2004, researchers at the University of Western Australia in Perth studied 3,987 males aged 71 to 89. The men provided demographic and health information and were tested for depression and cognitive difficulties. The researchers also checked the men's testosterone levels.
The 203 men who met the criteria for depression had significantly lower total and free (not bound to proteins) testosterone levels than those who weren't depressed. After controlling for other factors, such as cognitive scores, education level and body-mass index, the researchers concluded that men in the lowest quintile (20 percent) of free testosterone were three times more likely to have depression compared to those in the highest quintile.
While more research is needed to determine how low hormone levels may be linked to depression risk, the study authors believe it may be caused by changes in the levels of neurotransmitters or hormones in the brain.
"A randomized controlled trial is required to determine whether reducing prolonged exposure to low free testosterone is associated with a reduction in prevalence of depression in elderly men," the researchers wrote. "If so, older men with depression may benefit from systematic screening of free testosterone concentration, and testosterone supplementation may contribute to the successful treatment of hypogonadal (with low hormone levels) older men with depression."
Between 2 percent and 5 percent of people are affected by depression at any given time, according to background information in the study. Women are more likely than men to be depressed, but that difference disappears at about age 65. A number of previous studies have suggested that sex hormones may be a factor.
