VIENNA (FRONTLINE MEDICAL NEWS) Daily exposure to high-intensity light early in the morning resulted in significantly improved sexual satisfaction scores and a boost in testosterone levels in men with reduced libido or erection difficulty in a randomized, placebo-controlled clinical trial, Andrea Fagiolini, MD., said at the annual meeting of the American Thyroid Association.

“We found a very strong difference in sexual satisfaction and also in blood testosterone levels with intense light therapy. Patients seemed to respond to it really well, and our placebo group didn’t respond at all,” according to Dr. Fagiolini, professor and chairman of the department of psychiatry at the University of Siena (Italy).

“It’s still early to make a general recommendation. This was a small study. We need a larger trial with more patients. But if these results are confirmed, it would be very helpful because as of now we don’t have many tools to treat sexual dysfunction. So if light therapy works, I think it may be a better option than medications like Viagra [sildenafil] or similar drugs, which have side effects,” he said in an interview.

The trial included 38 men seen at the university urology clinic with a diagnosis of primary hypoactive sexual desire or sexual arousal disorder. Half were randomized to daily use of a white fluorescent light box for 30 minutes in the morning, preferably between 7 and 8 a.m. The light box, equipped with a UV filter, was the same as that used in treating seasonal affective disorder. Light therapy for seasonal affective disorder is an established therapy in the psychiatric world, one that has proved as effective as antidepressant therapy for that condition. It is “absolutely safe and tolerable,” except in patients with eye conditions or on photosensitizing medications, the psychiatrist noted.

The control group was on the same treatment schedule, but with light boxes that had been modified through the use of a neutral-density gel filter to provide a dose of just 100 lux instead of the 10,000 lux at a distance of 1 m from the light source to the cornea generated by the active therapy light box.

The study endpoints were change from baseline through 2 weeks of therapy on a self-administered rating of sexual satisfaction on a scale of 1-10, as well as testosterone levels.

From a baseline mean self-rated sexual satisfaction score of about 2, the group exposed to daily bright light for 2 weeks had a more than threefold increase to a score of 6.3, while the controls showed no significant change.

In addition, testosterone levels in the bright light group increased from 2.1 ng/mL to 3.6 ng/mL after 2 weeks, while remaining unchanged in controls.

“Our idea for this study came from the observation that sexual satisfaction is known to increase during the spring and summer, compared to fall and winter. We thought that may have something to do with the natural daylight,” Dr. Fagiolini said.

The most likely mechanism of benefit springs from the established finding that bright light stimulates the pituitary gland to produce leutinizing hormone. This results in increased levels of testosterone and inhibition of melatonin production by the pineal gland. Decreased plasma melatonin is thought to lead to reduced serum prolactin – and high prolactin has been linked to sexual dysfunction, he explained.

The trial was conducted in the fall and winter months to avoid confounding by more natural daylight during the other seasons. But if the study results are confirmed, this therapy might well be used year-round, the psychiatrist said.

He reported having no financial conflicts of interest regarding the study, which was conducted without external funding.