Circadian rhythm disorders

The natural internal clock that controls our 24-hour cycle of sleep and waking, circadian rhythms are easily upset by changes in schedule, and they're greatly affected by light and darkness. Jet lag is the best known circadian rhythm disorder, but this sensitive inner clock can also be disrupted by changes in routine resulting in an erratic sleep schedule.

What to do: If you suspect you have a circadian rhythm disorder, take steps to get your body onto a regular sleep schedule. Choose a bedtime and wake-up time that work for you, and follow the same routine each day, even on weekends. This can be tough for those who have to get up early during the week but like to stay up later on weekends, but do your best to craft a compromise between your work week and weekend habits. The important thing is to avoid the trap of sleeping from 10 p.m. to 6 a.m. during the week, then suddenly shifting to late nights and late mornings on the weekends. This will inevitably leave you with insomnia on Sunday night, which in turn sets you up to start the week exhausted on Monday morning.

The other technique experts advise is to stimulate your circadian rhythms with bright light and exercise during the day. Go outside for a stint of bright sunlight in the afternoon, and get some aerobic exercise each day. Helping your body feel more "awake" during the day resets your circadian clock so that your body is ready for sleep at bedtime.