SEATTLE—At first glance, bright light treatment, a regimen of light exposure at a specific intensity, seems promising. Among the conditions that have been reported to respond to such therapy are insomnia, depression, jet lag, seasonal affective disorder, mood disorders, and fatigue from working the night shift. However, virtually all studies of bright light treatment suffer from a major flaw—the failure to provide a detailed description of light delivery. Therefore, clinicians often end up devising their own light delivery methods, which may or may not result in consistent and effective treatment. Further, many research studies take place in the laboratory, where light delivery can be relatively easily monitored; the problems of standardization of treatment become much more difficult when treatment takes place in the home.

In view of this, Beatriz Hernandez and coworkers recently attempted to determine if any substantial variability in light delivery occurred during a 12-week home-based light treatment regimen—and indeed that is exactly what they found. Ms. Hernandez, a research coordinator in the Departments of Psychiatry and Behavioral Sciences at Stanford University in California, presented the study findings at the 16th Annual Meeting of the Associated Professional Sleep Societies.

LET THERE BE LIGHT

After being screened for major sleep, medical, or psychiatric disorders, the study subjects (27 adults with a mean age of 63.6) underwent a standard light treatment protocol. First, a research assistant visited their homes to set up either a dim (50-lux) or a bright (10,000-lux) lamp. Fifty lux is comparable to the light emitted from a desk lamp; 10,000 lux is similar to being outdoors on a sunny spring morning just after sunrise.

Curtains and shutters were closed during light administration, which occurred with subjects sitting directly in front of the lamp. The lamp was placed on a table covered with reflective white photographic paper, and the distance between the lamp face and the subject’s forehead was 18 inches.

In setting up the lamp, the lamp head was initially bent completely downward and then gradually rotated upward until the subject could see both light tubes through the ultraviolet filter. Each subject determined the minimum ambient light intensity necessary for personal safety to be used in conjunction with the lamp.

Light exposure measurements included 10 ambient light readings at each eye with a professional light exposure meter; the meter’s sensor was positioned in the direction of the subject’s gaze. With the subjects looking down at reading material (ie, not staring into the lamp), the investigators then switched the lamp on and took 10 more readings at each eye.

INTENSE DIFFERENCES

As expected, in home treatment settings the intensities of ambient, dim, and bright light were significantly different. However, significant differences were also detected for each type of light when baseline light exposure readings were compared with readings obtained at week 12 of treatment. The investigators also found substantial variability from baseline in the intensity of dim light readings taken at the study’s midpoint (week 5 or 6 of treatment).

It is possible that the subjects were responsible for at least some of the variability in light delivery. Those in the dim light group, for example, might have raised the head of the lamp to receive more light while those in the bright light group may have lowered it to receive less. “We do not know the extent to which this variability affects treatment outcome,” the investigators said.

Questions about the effectiveness of bright light therapy cannot be adequately answered without sufficient information on lamp setup or the amount of light subjects actually receive at the level of the eye, the investigators stressed. Their findings highlight the need to check the lamp placement during the course of treatment, they said.

—Timothy Begany

Suggested Reading
Martin SK, Eastman CI. Medium-intensity light produces circadian rhythm adaptation to simulated night-shift work. Sleep. 1998; 21:154-165.

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