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J Occup Environ Med. 2014 May;56(5):477-83. doi: 10.1097/JOM.0000000000000158.

Relationship between carbon dioxide levels and reported headaches on the international space station.

Author information

From the NASA Johnson Space Center (Dr Law, Ms Van Baalen, Dr Meyers, and Dr Alexander), Wyle Science, Technology and Engineering (Drs Foy and Wear), and MEI Technologies (Mrs Mason and Ms Mendez), Houston, Tex.

Erratum in

  • J Occup Environ Med. 2014 Sep;56(9):e82.



Because of anecdotal reports of CO(2)-related symptoms onboard the International Space Station (ISS), the relationship between CO(2) and in-flight headaches was analyzed.


Headache reports and CO(2) measurements were obtained, and arithmetic means and single-point maxima were determined for 24-hour and 7-day periods. Multiple imputation addressed missing data, and logistic regression modeled the relationship between CO(2), headache probability, and covariates.


CO(2) level, age at launch, time in-flight, and data source were significantly associated with headache. For each 1-mm Hg increase in CO(2), the odds of a crew member reporting a headache doubled. To keep the risk of headache below 1%, average 7-day CO(2) would need to be maintained below 2.5 mm Hg (current ISS range: 1 to 9 mm Hg).


Although headache incidence was not high, results suggest an increased susceptibility to physiological effects of CO(2) in-flight.

[Indexed for MEDLINE]

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