Headache symptoms and indoor environmental parameters: Results from the EPA BASE study

OBJECTIVE: The objective of this investigation was to determine the prevalence of migraine and headache symptoms in a national sample of US office employees. Also, we explored the association of headache symptoms with indoor environmental parameters of the work place. BACKGROUND: Sick building syndrome (SBS), which includes headache, is a common global phenomenon, but the underlying environmental cause is uncertain. MATERIALS AND METHODS: We used data from the 1994–1998 US Environmental Protection Agency's (EPA) Building Assessment and Survey Evaluation, a cross-sectional study of workers employed in 100 public and private office buildings across 25 states. The study used a self-administered questionnaire to assess headache frequency and prevalence of self-reported physician-diagnosed (SRPD) migraine. Indoor environmental parameters (IEP) were collected per EPA protocol from each building over a 1-week period and included carbon dioxide, carbon monoxide, temperature, relative humidity, particulate matter, volatile organic compound, illuminance, and sound level. The standards of American Society of Heating, Refrigerating and Air Conditioning Engineers were used to categorize IEP as either within- or out-of-comfort range for human dwelling. These limits delineate whether a parameter value is safe for human dwelling. Out-of-comfort range IEPs are associated with SBS and other human diseases. SRPD migraine and headache frequency were the primary outcome measures of the study. Multivariate logistic regression analyses were employed for the purpose of assessing the association between the outcome variable and IEPs. RESULTS: Of the 4326 participants, 66% were females and 60% were between 30 and 49 years. Headache frequency during the last 4 weeks was as follows: None in 31%, 1–3 days in 38%, 1–3 days per week in 18%, and every or almost every workday in 8%. Females had higher SRPD migraine prevalence compared to males (27% vs. 11%, P<0.001) and were more likely to report any headache in the last month compared to males (75% vs. 53%, P<0.001). Odds of SRPD migraine were higher (P<0.05) for those exposed to IEP out-of-comfort range, and odds of exposure to out-of-comfort range IEPs were higher in groups who reported higher headache frequencies. CONCLUSIONS: Migraine diagnosis and elevated headache frequency are associated with an uncomfortable indoor environment. Periodic assessments and adjustments of IEP may have a beneficial impact on employees who are vulnerable to SBS.