By April Chong

The potential health hazards associated with long flights, like dehydration, jetlag and deep vein thrombosis, are well known.

However, with people now spending more hours up in the air because of frequent travel, other risks have also come into play.

For one, back and neck pain can be a problem and travellers face more slipped disc-related injuries, observed Dr Bernard Lee, director of the Singapore Pain Care Centre.

In fact, 15 per cent of all new consultation cases at the centre are those who fly a lot for work.

The changes in cabin pressure may have some effects on spinal disc pressures and those who fly after spinal surgery have a higher likelihood of a spinal problem relapse, he explained.

Besides, economy class seats are not always ergonomic.

Dr Lee encourages travellers to move about after 45 minutes of being seated.

This can prevent a condition called piriformis syndrome in which the buttock muscles spasm and pull on the sciatic nerve, causing radiating pain in the lower body.

Frequent fliers also risk catching an infection within enclosed airplane cabins and through close contact.

The risk of infectious disease spreading can increase with increased exposure, said Dr Wong Sin Yew from Infectious Disease Partners.

However, how near one needs to be to get the germs from a sick person will depend on whether the infection is transmitted by droplets, which require close contact, or airborne, which can travel further, he added.

For example, the flu virus is transmitted via large respiratory droplets to people within a short distance and is unlikely to spread to the rest of the plane.

A more insidious risk is the levels of cancer-causing cosmic rays from the sun or outer space.

The intensity of cosmic radiation in an aircraft at cruising altitude is 100 times that at sea level. This is because the thinner layer of atmosphere at high altitude is less able to absorb cosmic radiation, said Dr Wong Seng Weng, the medical director at The Cancer Centre.

Hence, a 71/2-hour flight from Singapore to Sydney exposes one to cosmic radiation equivalent to a chest X-ray, he added.

A 1999 article in the medical journal Lancet found leukaemia striking more Danish cockpit crew who clocked more than 5,000 hours in the sky.

Pregnant women too may be more at risk as radiation is associated with negative effects on foetal development.

However, it would probably be of some concern only if a pregnant woman clocked more than 200 hours of air travel in the course of her pregnancy, said Dr Wong Seng Weng.

aprilc@sph.com.sg

This article was first published in Mind Your Body, The Straits Times.