Why early classes work against nature

Student life sometimes involves staying up late and waking up early, but students shouldn’t be blaming themselves for not getting to sleep early. The circadian rhythm is to blame.

The circadian rhythm is essentially “how the brain tells time,” said Mike Schwartz, a postdoctoral researcher.

Schwartz is working with assistant biology professor Horacio de la Iglesia, who is researching the circadian rhythms of mammals.

“The body has intrinsic rhythms which coordinate all its physiology with the environment,” Schwartz said. “It’s an important mechanism of survival.”

When these rhythms are not in orderly fashion, they can pose serious, and even fatal, problems, such as cardiovascular disease, cancer and psychiatric illnesses, Schwartz said.

Disrupted circadian rhythms can also lead to elevated levels of stress. The secretion of stress hormones, like melatonin, is controlled by the circadian rhythm.

“When you wake up in the morning, stress hormones are released to prepare your body for the day,” de la Iglesia said.

For students who find they are dozing off during the 8:30 a.m. lecture, the problem is a combination of both sleep deprivation and disruption of the circadian rhythm.

“It’s normal for teenagers and college students to go to sleep late,” Schwartz said. “Sleep-wake rhythms get delayed during the high school and college years.”

However, because college students are programmed to sleep later and must wake up earlier, they are not only depriving themselves of sleep, but they are also working against their circadian system.

“When students wake up early to go to class, there’s a lot of sleep disruption,” de la Iglesia said. “It’s out of phase with what their biological clock is telling them to do.”

Those who are frequent travelers or work night shifts also have disrupted sleeping rhythms. Disrupted sleeping rhythms can especially cause problems for those who work during the nocturnal hours, yet have “normal” schedules during the weekends.

“You’re asking them to work against their circadian rhythms,” Schwartz said. “It’s like asking them to go to New York and come back a couple times a week.”

People take four to five days to adjust to new sleeping rhythms, he said.

The same concept can also be applied to frequent travelers.

“When you are jetlagged, you are internally desynchronizing your circadian rhythm,” de la Iglesia said.

Using rodents as models for “desynchronization,” a term used when the circadian rhythm is disrupted, Schwartz and de la Iglesia are focusing on how the circadian rhythm controls sleep-wake cycles and various hormones in the body, including stress hormones.

“For humans, the most relevant rhythm is our sleep rhythm,” Schwartz said.

In humans, the circadian rhythm is regulated by pacemakers in the suprachiasmatic nucleus (SCN), which is located in the hypothalamus of the brain.

While there are other rhythms within the body working together to keep bodies in schedule, some of these rhythms are easily adaptable to changes in the external cues in the environment, while others are slower to respond. This can result in two sets of rhythms: one that is synchronized and another that is not.