Research report
Bright light improves vitality and alleviates distress in healthy people

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Abstract

Background: The relative shortage of light during the decreasing photoperiod may compromise well-being. Earlier studies suggest that bright-light exposure may be of help to alleviate winter-bound symptoms. Methods: We carried out a field study with exposure to bright light on office employees during winter. Results: Repeated bright-light exposure improved vitality and reduced depressive symptoms. The benefit was observed not only in healthy subjects with season-dependent symptoms but also in those not having the seasonal variation. Conclusions: Bright-light exposure during winter appears to be effective at improving the health-related quality of life and alleviating distress in healthy subjects. Clinical implications: Administration of bright light is a useful option to improve vitality and mood among subjects working indoors in wintertime. Limitations of study: Our field setting used self-reports, not interviews, for the assessment of outcome.

Introduction

Seasonal changes in mood and behaviour are frequent in the general population and affect predominantly women of reproductive age (Schlager et al., 1993). Ten to 15 percent of primary care patients in industrialised countries routinely complain of some difficulties in particular during winter. Whereas about 10% in a cohort of young adults suffer from low mood in winter over consecutive years (Wicki et al., 1992), only 0.2% of all patients and 3% of the depressed consulting their family doctor are diagnosed to have seasonal affective disorder (SAD) over one year (Blacker et al., 1997). Seasonal variation in well-being seems to decline with age, but still to persist into older age to a significant extent (Eagles et al., 1997; for review, see Partonen and Lönnqvist, 1998).

Atypical depressive symptoms (carbohydrate craving, prolonged sleep, weight gain, and increased appetite) can emerge in association with low illumination to which people are ordinarily exposed indoors, or even outdoors at high latitudes in wintertime, and compromise well-being in healthy subjects (Espiritu et al., 1994). Less consistent resetting of the circadian clock by light is thought to cause the associated circadian disturbances which tend to intensify with ageing.

Earlier studies suggest that exposure to bright light would alleviate the winter-bound symptoms (Kasper et al., 1988, Kasper et al., 1989). The objectives of our study were to measure the intensity of symptoms suffered by office workers during winter, and to analyse the effects of bright-light exposure on health-related quality of life and psychological distress.

Section snippets

Method

Our target population consisted of healthy adults working office hours. Subjects were recruited in October 1996 from three companies, yielding a study population of approximately 1250 persons. All subjects were naive to the explored intervention. We explained the study to the staff of the occupational health care centre of each workplace in a face-to-face meeting. A leaflet describing only the basic protocol was then delivered to all employees by the occupational health care centre staff. They

Results

Of the 160 enrolled subjects, 145 (91%) returned their questionnaires and entered the trial. Their mean (SD) age was 41.2 (9.0) years (range 22 to 62). Ninety-one (63%) of the respondents were women. Of the 145 respondents, 120 (83%) completed 4 weeks of intervention, 108 (74%) 8 weeks, 94 (65%) 12 weeks and 91 (63%) 16 weeks. Complete data on the outcome measures were received from 87 subjects. There was no significant difference in the baseline intensity of symptoms of psychological distress

Discussion

Our key finding was that repeated systematic exposure to bright light reduced the intensity of depressive symptoms among healthy subjects. Preliminary results from earlier studies have been disappointing, since the administration of bright light did not improve mood in three trials on 53 healthy subjects (Rosenthal et al., 1987b, Kasper et al., 1988, Kasper et al., 1990), or produced troublesome adverse effects in two trials on 29 subjects (Genhart et al., 1993, Bauer et al., 1994). Here, in

Acknowledgements

We are indebted to Ms Minna Havula-Eklund, BA, for technical assistance, to the personnel of the occupational health care centres for co-operation, and to Philips DAP for delivery of the devices used for research.

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