Disturbing the light-darkness pattern reduces circulating testosterone in healthy men.

This is an analytic-sagital-observational-endocrinological study of the environmental stress induced by disturbing the light-darkness pattern. A population of 15 males, ages 28-59 years old, participated at random. All had had a pattern sleep of 22:00-6:00 h. A blood peripheral sample was obtained in each between 8:00 and 9:30 h several days before 6 April 1997 (summer daylight change) (phase I). A second blood sample was obtained in the following 72 h right after 6 April 1997. No significant changes in estradiol levels were observed; however, on an individual basis 12/15 males showed a testosterone reduction ranging from 5.0 to 48.6%, and, on a group basis testosterone reduction was 4.5 +/- 1.3 vs. 3.5 +/- 1.0 (ng/mL) +/- SD, p = .05, comparing phase I vs. phase II. This finding shows the need to balance economical gain vs. changes in the health status of the population exposed to light-dark stress and may help slow the human biology deteriorating process.