| Abstract No.: | B-E2173 |
| Country: | Canada |
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| Title: | AGE AFFECTS CIRCADIAN ADAPTATION TO NIGHT SHIFT WORK |
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| Authors/Affiliations: | 1 Genevieve M. Tremblay*; 1 Diane B. Boivin; 1 Elaine Waddington Lamont; 2 France Varin;
1 Douglas Hospital, McGill University; 2 Faculty of Pharmacy, Montreal University, QC, Canada
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| Content: | Objectives: We previously demonstrated that the use of a judicious light/darkness schedule was an effective intervention to promoting circadian adaptation to night shift work. The aim of the present study was to assess the effectiveness of this approach in rotating shift workers.
Materials and Methods: 15 police officers on patrol working rotating shifts were studied in the laboratory before and after a series of 7 consecutive night shifts (8 to 8.5 h). Participants in the “intervention” group (n=8) were instructed to expose themselves to bright light (Litebook device) and to wear orange-tinted glasses from sunrise until bedtime (Blue-blockers, Telemedoptique Inc.). In the intervention group, an 8-hour daytime sleep episode was planned in total darkness 2 hours after the end of each shift. Workers in the “control” group (n=9) did not receive instructions regarding their light exposure or sleep schedule. Urine samples were collected every 3 hours for assay of urinary 6-suphatoxymelatonin (UaMT6s) during both 48-hour laboratory visits. The times of UaMT6 mid-point were determined for each visit as a marker of circadian phase and a phase shift was calculated between the two visits for each participant.
Results: Phase shift did not significantly differ between the two groups (Control: -5.78h ± 2.08, Intervention: -7.18h ± 1.26; one tailed t-test: p=0.29). The two groups did not differ in the timing of daily light exposure. Since some individuals in each group showed substantial circadian adaptation to the night-oriented schedule, subjects were reassigned to groups based on the median phase shift (observed at -6.45h). A two-tailed t-test revealed that the 9 police officers in the more shifted group were significantly younger (27.33 ± 2.83) than the 8 other police officers (33.13 ± 5.69, p=0.026).
Conclusion: The intervention provided in the present study did not result in a significant improvement in the degree of circadian adaptation to night shift. Since both groups were comparable in their pattern of light exposure, it could indicate insufficient exposure to the light device in the intervention group. Further analyses revealed that age is a contributing factor in the degree of circadian adaptation to night shift work.
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