Diseases & Conditions

Jet lag disorder

Jet lag, also called time zone change syndrome, is a sleep disorder that can affect anyone who quickly travels across multiple time zones. Jet lag is caused by a disruption to your body's internal clock or circadian rhythms — which tell your body when it's time to be awake and when it's time to sleep. The more time zones crossed, the more likely you are to experience jet lag.

Jet lag can cause daytime fatigue, an unwell feeling, difficulty staying alert and gastrointestinal problems. Jet lag is temporary but it can hinder your vacation or business travel. Fortunately, there are steps you can take to help prevent or minimize jet lag.

A disruption to your circadian rhythms
Jet lag can occur anytime you cross two or more time zones. Jet lag occurs because crossing multiple time zones puts your internal clock or circadian rhythms, which regulate your sleep-wake cycle, out of sync with the time in your new locale. For instance, you lose six hours on a typical New York to Paris flight. That means that if you leave New York at 4:00 p.m. on Tuesday, you arrive in Paris at 7:00 a.m. Wednesday. According to your internal clock, it's 1:00 in the morning, and you're ready for bed, just as Paris is waking up. And because it takes a few days for your body to adjust, your sleep-wake cycle, along with most other body functions, such as hunger and bowel habits, remains out of step with the rest of Paris.

The influence of sunlight
A key influence on your internal clock is sunlight. That's because the pineal gland, a part of the brain that influences circadian rhythms, responds to darkness and light. Certain cells in your retina — the tissue at the back of your eye — transmit the signal of light to an area of your hypothalamus, a part of your brain. The signal is then sent to your pineal gland. At night, the pineal gland releases the sleep-promoting hormone melatonin. During the day, melatonin production stops. So you may be able to ease your adjustment to your new time zone by exposing yourself to daylight in that new time zone.

Airline cabin pressure and atmosphere
Some research shows that the changes in cabin pressure associated with air travel may contribute to some symptoms of jet lag, regardless of travel across time zones. A July 2007 study published in the New England Journal of Medicine showed that simulated air travel at cabin pressures equivalent to 7,000 to 8,000 feet of elevation produced symptoms of altitude-related malaise (a feeling of unwellness), muscular discomfort and fatigue. In addition, most airline cabins circulate very dry air, which can be dehydrating. And mild dehydration can contribute to feelings of malaise, headache, and eye and nasal discomfort.

Jet lag usually doesn't require treatment. However, if you're a frequent traveler continuously bothered by jet lag, your doctor may prescribe medications or light therapy.

Medications

• Nonbenzodiazepines such as zolpidem (Ambien), eszopiclone (Lunesta) and zaleplon (Sonata)
• Benzodiazepines such as triazolam (Halcion)

These medications may help you sleep during your flight and for several nights afterward. Side effects are uncommon but may include nausea, vomiting, amnesia, sleepwalking, confusion and morning sleepiness. Although these medications appear to help sleep duration and quality, they may not diminish daytime symptoms of jet lag.

Light therapy
Your body's internal clock or circadian rhythms are influenced by exposure to sunlight, among other factors. When you travel across time zones, your body must adjust to a new daylight schedule and reset, allowing you to fall asleep and be awake at the appropriate times.

Light therapy can help ease that transition. It involves exposing your eyes to an artificial bright light or lamp that simulates sunlight for a specific and regular amount of time during the time when you are meant to be awake. This may be useful, for example, if you are a business traveler and are frequently indoors — away from natural sunlight — during the day in a new time zone. Light therapy comes in a variety of forms including a light box that sits on a table, a desk lamp that may blend in better in an office setting, a light visor that you wear on your head, and a dawn simulator that gradually makes a room brighter — simulating sunrise — which may help you wake up in the morning.

Sunlight
Use sunlight to reset your internal clock. It's the most powerful natural tool for regulating the sleep-wake cycle.

Plan ahead to determine the best times for light exposure based on your origination and destination points and overall sleep habits. An online jet lag calculator may make this task easier.

For example, a poor sleeper traveling from New York to Paris is advised to seek light between 11:30 a.m. and 2:00 p.m. on the first day in France and between 8:30 a.m. and 11:00 a.m. on the second day. By the third or fourth day, the traveler's internal clock should mesh with the local time. The results are even better if light exposure is combined with exercise such as walking or jogging.

Avoiding light at certain times is every bit as important as taking it in at others. The hypothetical New York to Paris traveler should avoid light from 9:00 a.m. to 11:30 a.m. on day one and from 6:00 a.m. to 8:30 a.m. on day two for best results. In the real world, that can be a challenge. At night, draw the blinds or drapes in your hotel room or use a sleep mask. During the day, dark glasses can help block out light.

Caffeine
Using caffeine, such as in the amounts you encounter in beverages like coffee, espresso and soft drinks, may help offset daytime sleepiness. However, it's best to time caffeine use so that it doesn't interfere with planned bedtime, because it may make it even more difficult to fall asleep or sleep well. So, for example, you may not want to consume caffeine within six hours of when you plan to go to bed.