CHICAGO (Reuters) - Brightening the lights for elderly people with dementia, in combination with a daily dose of the sleep hormone melatonin, improved their mood, sleep, and overall well-being, Dutch researchers said on Tuesday.

"The strong point of our findings was that effects were so prominent over a wide range of measurements of different aspects of functioning, suggesting a very strong improvement of the quality of life," said Eus van Someren of the Netherlands Institute for Neuroscience, in Amsterdam.

Dementia patients who live semi-independently often deteriorate and are forced into nursing homes as they lose mental and physical faculties, become irritable, suffer frequent headaches and develop sleeplessness.

The study found exposure to bright light during daylight hours — from the sun through large windows and from added fluorescent fixtures — decreased mental deterioration by five percent compared to patients not exposed.

There was a 19 percent relative reduction in depressive symptoms, and 53 percent relative slowing of their loss of ability to cope with daily living over the 15 months of the study, they reported in the Journal of the American Medical Association.