Whether working outside the home or as full-time caregivers, otherwise healthy women can feel fatigued. The reason may be a disruption of their melatonin, a neurohormone that regulates sleep patterns and one's sense of tiredness. High levels of melatonin enable you to sleep easier, while lower levels, caused by exposure to bright light, help you stay awake.
Disruptions in the melatonin cycle can mean health complications. It appears that regular production of melatonin may be important for a healthy immune system, for controlling stress and for guarding against cancer. With women entering the work force in ever-increasing numbers -- including shift jobs -- melatonin research will be of increasing importance to employers and their workers.
Q: How does melatonin affect feeling tired?
A: Melatonin works on a 24-hour cycle. When the cycle is disrupted, the body's internal clock is reset. For example, if the clock is reset by beginning work in a bright room at 10 p.m., the melatonin cycle starts the day again. Several days may pass before the melatonin levels adapt to the new schedule, providing needed rest.
If you feel tired after a full night's sleep, your melatonin production may be disrupted. Employees whose jobs involve alternating shifts, professionals or students working late into the night, caregivers, new mothers and jet-lagged travelers all are candidates for this situation.
Q: How does melatonin interact with work?
A: Melatonin levels drop when a person is exposed to bright light, such as in a factory, office or home. The mind stays alert, and rest becomes more difficult.
Regular melatonin cycles actually reduce the effects of stress. And frequent melatonin-cycle disruptions, such as those that may be experienced in shift work, can undermine the immune system, causing more frequent and longer-lasting illnesses. Disruptions in melatonin levels also appear to disturb the estrogen cycle. Some researchers believe an increased risk of breast cancer may result.
Q: Is there a way to keep my cycle balanced?
A: Researchers still are probing the answers to this interesting question. To help prevent jet lag, for example, astronauts are exposed to bright light for several days before a launch. New products are being developed that use timed exposure to light to help people's cycles function more smoothly.
Those who have to change their day-night routines should do so gradually. This can help keep their "internal clocks" balanced. Employers should schedule shift workers with an eye toward minimizing the time change.
A better-adjusted staff will be more productive, with less lost time and lower health-care costs.
Finally, understand that feeling tired is not a sign of weakness. The demands of the environment on your body may influence melatonin levels and make you tired. This could subject you to physiological changes, and health risks other than fatigue.
Dr. Matanoski is a physician and epidemiologist at the Johns Hopkins School of Hygiene and Public Health. She is founding director of its Institute for Women's Health Research and Policy.