Chronic alcohol consumption blunts the biological clock’s ability to synchronize daily activities with light, disrupts natural activity patterns, and continues to affect the body’s clock (circadian rhythm) days after drinking stops, a new study of hamsters found.
Alcohol consumption affects the master clock located in the suprachiasmatic nucleus (SCN) section of the brain. This clock controls the circadian cycle, a roughly 24-hour cycle that regulates sleeping and waking, as well as the timing of a variety of other physiological functions such as hormone secretions, appetite, digestion, activity levels and body temperature. The SCN synchronizes physiological functions so that they occur at the correct times and keeps these functions synchronized with daylight. Disruption of the clock dramatically increases the risk of developing cancer, heart disease and depression, among other health problems.
Researchers used hamsters to find out how alcohol affects circadian rhythms. Although hamsters are nocturnal, light synchronizes their clocks, just as it does in humans. The animals were divided into three groups that differed only in what they drank. The control group received only water. A second group received water with 10% alcohol and the third group received water with 20% alcohol. Hamsters, given a choice, prefer alcohol, which they metabolize quickly.
The hamsters that drank alcohol had the hardest time changing their rhythms after being exposed to the dim light, and the more alcohol they drank, the harder it was to adjust. The hamsters that drank only water woke up 72 minutes earlier than they normally would when exposed to dim light. The 10% alcohol group woke up 30 minutes earlier and the 20% alcohol group woke up only 18 minutes earlier.