Asthma and depression: the Cooper Center Longitudinal Study

Abstract

Background

Prior research suggests a possible association between asthma and depression.

Objective

To examine the association between asthma and depressive symptoms, controlling for asthma medications, lung function, and overall health.

Methods

We conducted a cross-sectional study of 12,944 adults who completed physician-based preventive health examinations at the Cooper Clinic from 2000 to 2012. Information on medical histories, including asthma and depression, and medications were collected. Participants reported overall health status, completed spirometry testing, and underwent depression screening using the 10-item Center for Epidemiologic Studies Depression Scale (CES-D). Dependent variables of current depressive symptoms (CES-D scores ≥10) and lifetime history of depression were separately modeled using logistic regression with independent variables, including demographics, spirometry, asthma controller medications, and patient-reported health status.

Results

The sample was predominantly white and well educated. The prevalence of asthma was 9.0%. Asthma was associated with an odds ratio (OR) of 1.41 (95% CI, 1.16-1.70; P < .001) of current depressive symptoms based on CES-D score. Asthma was also associated with lifetime history of depression (OR, 1.66; 95% CI, 1.40-1.95; P < .001). Neither lung function nor asthma controller medications were significantly associated with depression.

Conclusion

Asthma was associated with increased prevalence of current depressive symptoms and lifetime depression in a large sample of relatively healthy adults. These findings suggest that the increased likelihood of depression among patients with asthma does not appear to be exclusively related to severe or poorly controlled asthma. People with asthma, regardless of severity, may benefit from depression screening in clinical settings.

Introduction

Asthma and depression each affect an estimated 8% to 12% of the population and cause significant morbidity and mortality.[1], [2], [3] Both illnesses are challenging to treat. People with both depression and asthma have increased asthma-related emergency department visits, physician visits, days with asthma symptoms,⁴ mortality and morbidity, health-related work disability, and costs to employers due to lost work days⁵ and decreased work performance compared with those with asthma but without depression. Hakola et al⁶ observed that, compared with their healthy counterparts, employees with asthma and depression had a 4.5 times higher risk of work disability. All of these factors contribute to substantial economic costs to both the patient and society.⁶

Several epidemiologic studies[2], [7], [8], [9], [10], [11], [12] have reported an association between asthma and depression. World Healthy Survey data revealed significant associations between asthma and depression in 35 of 54 countries. However, the odds ratios (ORs) ranged widely across regions, from a nonsignificant 0.5 in Senegal to a high of 18.4 in Comoros.⁷ Global health care disparities and differences in disease reporting might explain the variation in reported associations in this report.[2], [7], [8], [9], [13], [14], [15], [16] The World Healthy Survey data did not include the United States, and the limited data on the association between asthma and depression in US populations have relied on patient self-reports of asthma and depression.

Single-country studies that assessed asthma and depression, using methods other than self-report, have focused on young people, not a broad age range of adults, and have revealed mixed results.[17], [18], [19] Lev-Tzion et al¹⁷ evaluated 195,903 Israeli men who underwent military service eligibility evaluations and found that people with asthma were more likely to have mood and anxiety disorders than those without (OR, 1.31; 95% CI, 1.19–1.46). During recruitment, asthma was diagnosed based on medical record history of previous diagnosis or history of wheezing with those with positive responses then receiving assessment by a pulmonologist that included history, physical examination, and spirometry. A depression diagnosis was based on previous medical history and psychiatric screening and evaluation. Hayatbakhsh et al¹⁸ assessed 2,443 Australian young adults (ages 18-24 years) for psychiatric disorders and found that both self-reported asthma and asthma medication use were significantly associated with lifetime major depressive disorder (MDD) (P < .001), but reduced lung function (forced expiratory volume in 1 second [FEV₁]) was only significantly associated with increased depression among males.¹⁸ Finally, Goodwin et al³⁶ found in an asthma cohort (N = 2,193) in Western Australia that severe, but not mild, asthma at 5 years of age significantly increased the likelihood of mental health problems presenting later in youth (ages 5–17 years).

Smaller cohort studies (N < 743) of adults that assessed lung function, asthma severity, asthma control, and quality of life also had mixed results. Most studies found significant associations between depression and increased asthma severity, depression and poor asthma control, or depression and decreased quality of life in people with asthma.[13], [20], [21], [22], [23], [24] These cohorts, which included primarily moderate to severe asthma, attribute asthma disease burden to the associated increased rates of depression.[13], [20], [21], [22], [23], [24], [25] Conversely, Goodwin et al²⁶ examined adults (N = 4,181) using the Composite International Diagnostic Interview and did not find an association between either severe asthma or nonsevere asthma and depression.²⁶ Thus, the association between asthma severity and depression remains unclear.

The current report describes patients who underwent fee-for-service preventive medical evaluations in the Cooper Center Longitudinal Study (CCLS) to examine depression and asthma in a US sample of mostly healthy people from across the adult age spectrum. To our knowledge, this is the first large sampling of US adults with asthma to explore the prevalence of depression in people in generally good physical health and with relatively high socioeconomic status. The previous population surveys largely relied on relatively subjective measures, such as self-report of asthma. The current study goes beyond patient self-reports to include physician-verified asthma diagnosis, objective measures of lung function and asthma medication use, and a standardized, well-validated depression assessment. In addition, the report minimizes confounding factors, such as physical disability, poor access to health care, and low household income, that may affect the association between an asthma diagnosis and depression.