High Prevalence and Clinical/Sociodemographic Correlates of Miscarriages Among Flight Attendants

There are many occupational health hazards associated with long hours of air travel, including cosmic radiation exposure, circadian rhythm disruptions, prior and secondhand smoke exposure, for flight attendants who flew before smoking bans were initiated in the 1990s. Previous studies in flight attendants have found increased incidence of breast cancer and melanoma. However, there is little information on the relationship of airline travel and reproductive health in flight attendants. Secondhand smoke exposure has numerous negative health effects, such as increased cardiac events and respiratory infections, but its effect on reproductive health is not known. This study seeks to examine the role of secondhand smoke exposure on the miscarriage rate in flight attendants who flew before the smoking ban.

Flight attendants who flew before the smoking ban and participating in a study of health effects of secondhand smoke were asked to complete a reproductive health survey. We compared miscarriage rates of flight attendants to the general population using 2010 data from the Centers for Disease Control and Prevention.

In our cohort of 145 female flight attendants exposed to secondhand smoke, there were 45 miscarriages (26%), compared with a 17.1% rate in the Centers for Disease Control and Prevention report (P = .002). There was no difference in secondhand smoke exposure between the flight attendants with miscarriage and the group without miscarriage (P = .93).

This study found an increased incidence of miscarriage in flight attendants, which was unrelated to secondhand smoke exposure. Other factors, such as circadian rhythm disruption and radiation, may be related to these reproductive health findings and require further investigation.

There is increasing recognition of the occupational hazards associated with long hours of air travel. The recognition of the association of secondhand smoke exposure and health problems led to successful efforts by flight attendants to have smoking banned on airplanes in the 1990s.1, 2 Secondhand smoke exposure is associated with an increased risk of lung cancer, coronary heart disease, and stroke.3, 4 We have previously shown that flight attendants exposed to secondhand smoke have an association between secondhand smoke exposure and increased rates of hypertension,5 as well as increased rates of respiratory illnesses compared with the general population.6 Before airline smoking bans it is estimated that secondhand smoke exposure of flight attendants in aircraft cabins was 6 times that of the average worker and 14 times that of the average person.7 In addition to secondhand smoke exposure, other health-related factors, such as circadian rhythm disruption, are associated with flying.8 Serum melatonin levels are a marker for disruption of circadian hormone production. In a prior study of flight attendants and teachers, flight attendants were found to have higher adjusted melatonin levels.8 Therefore traveling through many time zones is an adverse health exposure for flight attendants. The time changes can have 3 major effects on circadian rhythms: desynchronization between external time cues and internal physiologic rhythms, disruption of internal physiologic rhythms relative to each other, and resultant sleep loss.9 Pilots and flight attendants are also exposed to ionizing radiation while logging many flight hours. As a profession they have one of the highest occupational radiation exposures.9 At aircraft altitudes of 25,000 or more feet, primary cosmic radiation interacts with molecules of the atmosphere and generates secondary and tertiary radiation. These types of radiation include neutrons—known human carcinogens10, 11—as well as charged particles with high relative biological effectiveness. Large-scale analyses have examined the incidence of breast cancer and melanoma among flight crewmembers.12, 13 These studies found a significantly increased risk for melanoma, breast, and bone cancer among female flight attendants. However, there are currently no official radiation dose limits for flight crew members in the United States.

During our previous work with flight attendants and secondhand smoke exposure, we observed that airline crew members seemed to have more miscarriages than the general population. To measure any effects on reproductive health in flight attendants who flew before the smoking ban, we surveyed our cohort of flight attendants to determine whether their miscarriage risk is increased compared with the general population.