SEATTLE — Dana Groff, a program manager at Microsoft Corp. in Redmond, Wash., who was having trouble sleeping, got an unusual prescription when he went to the doctor: a light bulb.

Not just any light, but a set of high-intensity, full-spectrum bulbs that Microsoft paid $1,000 for as part of a new benefit. "I get into work and I feel better than I do at home, where I'm dragging," says Groff, 43, who says his sleep disorder was aggravated by the lack of daylight in Seattle, where the sun rises at 8 a.m. and sets by mid-afternoon this time of year.

A dearth of sun has been linked to sleep disorders and a form of depression known as SAD, or seasonal affective disorder. In Seattle, where it's cloudy for 86 days on average — or 72 percent of the time — from November through February, more workers are using prescribed sunlamps at work.

About 10 percent of Seattle-area residents suffer from a severe case of SAD during the shortest days of the year, says David Avery, a psychiatry and behavioral sciences professor at the University of Washington. As many as 20 percent more sleep longer in winter, have trouble waking and lack energy.

In northern climates from Scandinavia to Canada, the lack of sunlight during the shortest days of the year has been linked to increased rates of depression, suicide and alcoholism. Seattle is located at 47 degrees latitude, closer to the North Pole than Toronto or Boston.

"Depression increases with latitude and cloud cover," says Avery, 59, who's studied SAD for 25 years.

At the Indoor Sun Shoppe in Seattle, a seller of sunlamps, briefcase-sized light-therapy boxes and dawn simulators that gradually brighten rooms, about 90 percent of sun-therapy products are sold from mid-October through January. Sales are about 20 percent ahead of last year, says Shaun Murphy, the store manager. The store charges $169 to $559 for the equipment.

"We get a lot of people who come from brighter places, transplants from California and Florida," says Murphy, 34.

Light boxes emit as much as 10,000 lux, a unit of illumination that refers to the power of light, more than the 100 lux in a typical living room. SAD sufferers typically spend at least 30 minutes a day under a light box.

Waking at 6 a.m. in Seattle is like a jolt in the middle of the night, Avery says. A dawn simulator can help ease transitions from sleep to arousal by signaling the body to cut production of the hormone melatonin, which is secreted when it's dark.

Seattle employers are becoming more accommodating to light-starved workers. Cliff Sanderlin, director of development at the non-profit environmental group People for Puget Sound, says he bought a full-spectrum lamp for his desk after watching a colleague use one to combat seasonal depression.

"I turn that on first thing in the morning," says Sanderlin, 59, who notices that his energy level wanes as days get shorter.

SAD can carry a stigma because of its link to depression, says David Goodenough, 60, who counsels workers and employers in Seattle about human resources issues. His business picks up about 15 percent beginning in November.

"If you tell someone you get sad because there's no sunlight, the vast majority of people are going to say, 'Yeah, I like sunshine, too,' " Goodenough says.

Insurance carriers such as Hartford, Conn.-based Aetna Inc. are beginning to offer the phototherapy benefit because SAD leads to lost productivity for employers and the treatment can be relatively inexpensive, says Cindy Gates, a vice president at insurance consultant Aon Corp. in Baltimore. Aetna declined to name clients that offer the benefit.

About 200 of Microsoft's 30,000 Seattle-area employees have taken advantage of the light therapy benefit since the company began offering it of this year, says spokesman Lou Gellos.

Groff's office, equipped with lights that emit about 3,000 lux, or six times the amount of illumination in an average office, attracts visitors.

"I've had people deliberately want to have a meeting in my office," Groff says.