To the editor:
Natural and anthropogenic disaster-related experiences can exacerbate background stressors, which may lead to negative mental health outcomes [1]. However, few studies have assessed mental health indicators related to measured lung function in the aftermath of a disaster. In 2010 the Deepwater Horizon (DWH) disaster resulted in the largest maritime oil spill in US history and negatively affected proximal communities, which experienced increased distress and post-traumatic stress disorder (PTSD)-like symptoms attributed to the disaster[2, 3]. We investigated the relationship between mental health indicators and lung function following this disaster.
METHODS
Participants
We used cross-sectional data from the Gulf Long-Term Follow-up Study (GuLF Study), a prospective cohort of adults (n=32,608) who participated in response and cleanup activities following the 2010 Deepwater Horizon (DWH) oil spill, and others who received worker safety training but were not hired [4]. Enrolled participants completed telephone interviews between March 2011 and March 2013. Participants who were English- or Spanish- speaking residents of Alabama, Florida, Louisiana, Mississippi, or Texas (n=25,304) were eligible for a home visit exam. 11,193 eligible participants completed a home visit exam (May 2011-May 2013) and of these, 10,040 completed spirometry testing. We analyzed spirometry data from participants with spirometry tests meeting American Thoracic Society/ European Respiratory Society (ATS/ERS) quality standards [5]. All home visit participants provided written informed consent. This study was approved by the National Institute of Environmental Health Sciences Institutional Review Board (IRB).
Mental health indices
Participants completed psychological assessments on multiple mental health endpoints using validated questionnaires. Recommended standardized cut-points were used to classify participants. Perceived stress was measured at enrollment using Cohen’s perceived stress scale (PSS) and being positive for stress was defined as having a score ≥ 9 (Range =0–16) [6]. The remaining tests were measured at the home visit. Depression was measured using the PHQ-8 tool and defined as having a score ≥ 10 (range=0–27) [7]. Generalized anxiety disorder was measured using the GAD-7 and defined as having a score ≥ 10 (range=0–21) [8]. Finally, PTSD was measured using the PC-PTSD screener and defined as having a score ≥ 3 (range=0–4) [9].
Pulmonary function
Home visit participants performed spirometry using an ultrasonic spirometer (EasyOne™, ndd Technologies, Andover, MA) administered by trained examiners. Lung function outcomes of interest included the forced expiratory volume in one second (FEV1, milliliters), forced vital capacity (FVC, milliliters) and their ratio (FEV1/FVC,%). Tests for 10,019 participants (workers and non-workers) were overread by a spirometry expert for quality control and 7,487 met the ATS/ERS within- and between- maneuver acceptability criteria, defined as at least 3 acceptable maneuvers, with variability of either FEV1 or FVC ≤150 mL or equivalent quality deemed by a spirometry over-reader expert (defined as having a score of either A, B or C)[5]. After excluding participants with missing information on any mental health outcome (N=833) and excluding participants with missing covariate information (N=858; 49% of which were missing income data) the final analytic sample was 5,796.
Potential confounders
Information on demographic, socioeconomic, lifestyle, and health measures were collected at enrollment using a structured telephone interview. Anthropometric measures including height and weight, were obtained by examiners at the home visit. Potential confounders were selected using a directed acyclic graph and included age at home visit (years), sex (male, female), height at home visit (cm), weight (lbs), race (white, black, other), ethnicity (Hispanic, non-Hispanic), smoking status (current heavy, current light, former, never), and secondhand smoke exposure (yes, no), education level (Less than High School/Equivalent, High School Diploma/GED, Some College/2 Year Degree, 4 Year College Graduate or more), and income level (<$20,000, $20,000-$50,000, >$50,000). Height squared (cm2) was included in models based on its reported quadratic relationship to lung function measures [10]. We also controlled for pre-existing lung disease (doctor’s diagnosis of bronchitis, emphysema, or asthma; yes, no), oil spill response and cleanup work hierarchical job class (response work, operations, decontamination, cleanup on water, cleanup on land, non-worker). Finally, we adjusted for area deprivation using a published index linked to participant home visit addresses [11].
Statistical analysis
We evaluated the relationship of each mental health outcome (PTSD, depression, stress and anxiety) to the lung function measures. We modeled mental health outcomes separately, treating each as an independent variable and adjusting for age, sex, race/ethnicity, height (cm), height2 (cm2), weight, smoking, secondhand smoke, income, education, neighborhood deprivation, pre-existing lung disease, and oil spill response and cleanup work jobs in each model. All analyses were conducted using SAS v 9.4 (SAS Institute, Cary, NC).
RESULTS
Perceived stress and PTSD symptoms were not associated with any lung function measure (Table 1). Compared to those without depression, those with severe depression scores had a higher FEV1(β: 61 mL, (95% CI: 21, 101)) and FVC (β: 62 mL, 95% CI: 16, 109), but not FEV1/FVC ratio. Participants with severe generalized anxiety disorder scores versus those without also had higher FEV1(β: 78 mL, (95% CI: 44, 113)), FVC (β: 71 mL, (95% CI: 31, 112)), and the FEV1/FVC ratio (β: 0.56%, (95% CI: 0.15, 0.97)).
Table 1.
Adverse mental health outcomes and lung function, GuLF Study participants (2011–2013) (n=5,796)
| FEV1, mL | FVC, mL | FEV1/FVC, % | ||
|---|---|---|---|---|
| Mental health outcomes | N(%) | Mean Differences (95% CI)a | Mean Differences (95% CI)a | Mean Differences (95% CI)a |
| Perceived stress (PSS) | 1524(26) | 2(−31,35) | 5(−34,44) | −0.05(−0.44,0.35) |
| Post-traumatic stress disorder (PTSD) symptoms | 280(5) | 14(−52,80) | −5(−82,72) | 0.58(−0.20,1.36) |
| Depression | 894(15) | 61(21,101) | 62(16,109) | 0.32(−0.15,0.79) |
| Generalized anxiety (GAD) | 1290(22) | 78(44,113) | 71(31,112) | 0.56(0.15,0.97) |
All models adjusted for: age, sex, race, ethnicity, height, height2, weight, smoking, secondhand smoke, educational level, income, area deprivation, pre-existing lung disease (bronchitis, emphysema, asthma), and oil spill response and cleanup work jobs.
Mental health outcomes were modeled separately; models are not mutually adjusted for other outcomes
DISCUSSION
We examined the relationship between adverse mental health measures and lung function in a large population of adults living in US Gulf states enrolled in a cohort following the 2010 DWH disaster. Despite findings of adverse mental health outcomes associated with response and cleanup work following the Deepwater Horizon disaster [2], results here indicate better lung function associated with severe depression and generalized anxiety.
Our results are discordant with the existing literature on depression and anxiety, which has reported links between mental health and/or stress and poor respiratory health. Psychological stress can lead to hyperresponsiveness of the hypothalamic pituitary axis, increasing secretion of inflammatory cytokines and the release of cortisol that may trigger hormones (e.g. corticotrophin)[12]. This can potentiate the immune system, or autonomic control resulting in bronchoconstriction [13]. Higher depression scores have been associated with lower FEV1 [14] while war-related stressors have been associated with increased risk of asthma [15]. It is unclear why we observed better lung function for those with depression and generalized anxiety. Results may be attributable to uncontrolled confounding, such as lack of data on clinical management of stress, or limitations of this cross-sectional analysis. Findings for PTSD symptoms agree with a prior study that found no association between PTSD and lung function measures, although the authors did find an association with asthma [16]. In that study, traumatic stress was associated with modestly lower FEV1 and FEV1/FVC ratio measures. Given the dearth of information on specific mental health disorders and adverse respiratory health and inconsistent results across studies, prospective studies are needed to clarify this relationship.
Acknowledgements:
Thank you to Dr. Symielle Gaston and Dr. Thanh Hoang for reviewing an earlier draft of this manuscript.
Sources of Financial Support:
This research was funded by the Intramural Research Program of the NIH, the National Institute of Environmental Health Sciences (Z01 ES 102945).
Footnotes
Conflicts of Interest: None declared
Code: The data are not available for replication.
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