The effects of coffee consumption on sleep and melatonin secretion.
BACKGROUND
In this study we examined the effects of caffeine on sleep quality and melatonin secretion. Melatonin is the principal hormone responsible for synchronization of sleep. Melatonin secretion is controlled by neurotransmitters that can be affected by caffeine.


METHODS
In the first part of the study, six volunteers drank either decaffeinated or regular coffee in a double-blind fashion on one day, and the alternate beverage 7 days later. Sleep parameters were assessed by actigraphy. In the second part of the study, the subjects again drank either decaffeinated or regular coffee, and they then collected urine every 3h for quantitation of 6-sulphoxymelatonin (6-SMT), the main metabolite of melatonin in the urine.


RESULTS
We found that drinking regular caffeinated coffee, compared to decaffeinated coffee, caused a decrease in the total amount of sleep and quality of sleep, and an increase in the length of time of sleep induction. Caffeinated coffee caused a decrease in 6-SMT excretion throughout the following night.


CONCLUSIONS
The results of our study confirm the widely held belief that coffee consumption interferes with sleep quantity and quality. In addition, we found that the consumption of caffeine decreases 6-SMT excretion. Individuals who suffer from sleep abnormalities should avoid caffeinated coffee during the evening hours.
Department of Medicine C, Meir Hospital, Sapir Medical Center, and the Sackler School of Medicine, Tel-Aviv University, Kfar-Saba 44281, Israel. lotansh@ccsg.tau.ac.il
Lotan
L
Shilo
Hussam
H
Sabbah
Ruth
R
Hadari
Susy
S
Kovatz
Uzi
U
Weinberg
Sara
S
Dolev
Yaron
Y
Dagan
Louis
L
Shenkman