One moment you are staring out of the window, noticing other flights in their hangars and the next you find everything falling behind with a tremendous rush, and you zoom from the ground to 20,000 feet in the air within minutes! The first flight is always a wonderful experience for many, which of course, is coupled with a sudden jolt of fear and excitement. But what most people are unaware of is that frequent flying has its own share of ill effects on health. Humans are terrestrial organisms who are biologically designed to function and exist comfortably close to sea level. So every time we enter a climate that is beyond what we normally inhabit, we become susceptible to certain risks or dangers that can impact our health. How Can Flying Impact Our Health? When we speak of flying, several factors come into the picture, most common being atmospheric pressure, gas concentrations, temperature, and most important of all, altitude. Flying exposes our body to deal with each of these elements which behave differently when we are close to sea level. # For long-haul passengers and frequent fliers, the most obvious side effect is what is known as jet-lag. This problem occurs when the body's internal clock (the clock tells you when it is time to sleep and to be awake) is disrupted due to crossing multiple time zones within a short period (for instance, flying east to west or west to east). Jet lag can trigger:

• Sleep disorders
• Digestive distress
• Loss of appetite
• General feeling of malaise
• Abnormal fatigue during daytime
• Muscle soreness
• Concentration problems
• Memory problems
• Anxiety
• Irritability
• Headaches
• Irregular menstruation

# A health risk that divers should be wary of before flying is decompression sickness. This condition can trigger unpleasant and sometimes severe symptoms in people who fly shortly after diving. Common symptoms may include:

• Deep, sharp pain; normally localized
• Itching, and swelling of the skin
• 'Pins and needles' sensation, numbness or seizures
• Confusion
• Vision problems
• Weakness
• Paralysis in the legs
• Headache, abnormal fatigue
• Loss of balance
• Hearing loss
• Labored breathing
• Dry cough

# Altitude sickness is another health hazard for people who fly frequently. Also known as acute mountain sickness (AMS), this problem occurs when one does not receive enough oxygen while going quickly from lower altitudes to 8,000 feet or higher. Symptoms caused by this condition may include:

• Throbbing headache
• Weakness and abnormal lethargy
• Loss of appetite
• Dizziness
• General feeling of malaise

Although most modern passenger aircraft are designed to maintain a cabin altitude of about 8,000 feet, most long-haul fliers still experience some of these symptoms. Some people compared the effects of altitude sickness as similar to that of a hangover. Symptoms such as disorientation, unsteady gait, fainting, and lips or nails turning blue or gray indicate a severe case of altitude sickness. # One common physiological effect that is felt during a flight, especially in a long-haul one, is dehydration. Most aircraft cabins have a relative humidity which is less than 20%. This is to keep the structure and avionics of the aircraft from any harm that can arise from condensation. This humidity is, however, lower than what is required by the body to avoid dehydration (more than 30%). That is why it is common for fliers to experience symptoms such as:

• Dry and scratchy eyes
• Dry skin
• Breathing problems for people with conditions like asthma
• Sticky mouth
• Constipation
• Headache
• Sunken eyes
• Unconsciousness (in case of severe dehydration)

Low humidity can also make people more susceptible to contract respiratory infections. These symptoms could be more severe for people who undertake frequent flying trips unless they constantly hydrate themselves. # The ascent and descent of a flight causes the gases trapped in the body to expand and contract respectively. This causes a difference between the air pressure in the middle ear and air pressure in the environment. This condition is known as airplane ear or ear barotrauma. Its common symptoms include:

• Mild to severe ear pain
• Feeling of something blocking the ear canal
• Ringing in the ear
• Vertigo
• Vomiting

In severe cases, passengers may also bleed from their ear, encounter hearing loss, experience tooth pain or pain in the gastrointestinal tract. # Most experts consider deep vein thrombosis (DVT) to be a possible health risk of frequent flying, especially for people who undertake long distance travel. This condition occurs when a blood clot forms in one or more of the deep veins in the body, commonly in the legs. The main cause of the problem is being stationary or sitting still for a long time while flying or traveling by car. In healthy individuals, the blood clot is normally dissolved by the body without causing any long-term effects. But if the blood clot is large and it does not dissolve on its own, then it may break loose, travel through the bloodstream and lodge in the lungs blocking the blood supply. This is known as pulmonary embolism, which can prove fatal if not treated immediately. The odds of developing DVT while traveling, however, is usually less unless accompanied by one or more risk factors such as pregnancy, medical history of DVT or pulmonary embolism, cancer, blood-clotting disorders, or use of hormone replacement therapy. # While jet lag is a familiar term for almost all fliers, cosmic radiation is usually unheard of. Cosmic rays are highly energetic particles that originate in outer space and bombard the earth. But thanks to the earth's atmosphere and magnetic field, cosmic radiation accounts for only 8% of the total radiation we receive annually. Having said that, the more we move away from our atmosphere towards outer space, the more susceptible we become to this radiation. So given this fact, people who fly frequently are exposed to more cosmic radiation than those who seldom fly or do not fly at all. Research suggests that pilots and aircrew are exposed to 4.6 millisieverts (mSv) of radiation a year compared to radiation workers in ground-based industries, in whose case the exposure is 3.6 mSv. As aircrew and people who fly at least once or twice a week are exposed to higher radiation levels over time, they may be more susceptible to skin cancer, leukemia or prostate cancer. Current studies, however, show that the odds of developing cancer from cosmic radiation is lesser than other factors that we encounter at ground level. Also, some studies have shown no significant health effects of the radiation on either aircrew or passengers. Other Problems of Frequent Flying

• Brief episodes of psychosis
• Exposure to pollutants such as ozone, breathing air mixed with jet oil, and combustion products of jet fuel
• Food poisoning
• Transmission of infections such as common cold and flu through the aircraft air filtering systems
• Flight phobia
• Mental stress

Frequent flying is something that is inevitable for business people who are always on the go. And speaking of pilots or aircrew, the above health risks can be attributed as occupational hazards. Most of these risks may not usually bother people who are otherwise healthy but they may be a concern for those with certain chronic medical conditions. So consulting their general practitioner or doctor before embarking a flight, especially a long-haul one may provide some help in reducing some of these health risks. Bon voyage!