Summary

Background: Occupational asthma (OA) is a significant occupational health problem impacting the employment sector, health care resources, and the individual. From 10 to 30% of all adult-onset asthmatics mention that their asthma worsens at work, and is often difficult to diagnose and treat. The majority of patients referred for evaluation of OA (approximately 70%) do not receive a diagnosis of OA, and as many as 30% of them will fail to receive a final diagnosis of any medical (i.e., biological) disorder. However, these patients will remain symptomatic and unable to work. Though several differential diagnoses are considered (e.g., rhinitis, eosinophilic bronchitis, hyperventilation syndrome), psychiatric disorders (many of which present with somatic complaints that may mimic asthma such as panic disorder and hypochondriasis) are rarely, if ever, assessed. This suggests that a significant number of patients will not be diagnosed or offered appropriate treatment that may help them return to a normal level of functioning, including returning to the workforce. Failing to detect psychiatric morbidity in these patients may also have important implications for health service use. Left undetected and untreated, patients with psychiatric disorders are likely to continue being symptomatic, increasing their risk for health service use such as emergency department and physician visits, at a high cost to both them personally and the society.

Objectives: The primary objective of this study was to assess rates of psychiatric disorders (including mood and anxiety disorders, and hypochondriasis) and levels of psychological distress among patients under investigation for OA. The secondary objective of this study was to determine the impact of psychiatric morbidity on employment status, health service use and quality of life at 12-18 month follow-up. 

Methods: A total of 219 consecutive patients (59% male, mean age 42 ± 11.1 years) underwent a sociodemographic and medical history interview on the day of their OA evaluation, which included spirometry and specific inhalation challenge testing. The Primary Care Evaluation of Mental Disorders (PRIME-MD) was used to assess mood and anxiety disorders, and patients completed the Whiteley Hypochondriasis Index (WI) to assess clinical levels of hypochondriasis. Patients also completed a battery of self-report questionnaires assessing levels of psychological distress including the Beck Depression (BDI-II) and Beck Anxiety (BAI) Inventories, and the Anxiety Sensitvity Index (ASI). Patients were re-contacted approximately 12-18 months later to assess employment status, health service use, and quality of life.

Results: Data were available for 196 patients, of which 152 (78%) met criteria for at least one diagnosable disorder. Final diagnostic results revealed that 26% (n=50) of patients had OA, 25% (n=48) had asthma or work-exacerbated asthma, 14% (n=28) had another inflammatory disorder, 13% (n=26) had a non-inflammatory disorder, and 22% (n=44) did not have a diagnosable disorder. A total of 34% (n=67) of the sample met criteria for a current psychiatric disorder; mood and anxiety disorders affected 29% (n=56) and 24% (n=47) of the sample respectively, and 6% (n=12) had scores on the WI suggestive of hypochondriasis. Levels of depression, anxiety and anxiety sensitivity were in the normal range and did not differ according to diagnostic group. Interestingly, while overall rates of psychiatric disorders were only marginally more common among patients without (45%) relative to those with (31%) a diagnosis (F=3.12, p=0.079), rates of hypochondriasis were significantly more common among patients without (14%) relative to those with (4%) a diagnosis (F=5.71, p=0.018). Moreover, meeting criteria for hypochondriasis significantly increased the likelihood of not receiving a final diagnosis by nearly 4-fold (adjusted OR=3.92, 95% CI=[1.18;13.05], p=0.026). Follow-up results indicated that after adjustment for covariates (including diagnostic group), patients with versus without a psychiatric disorder at baseline had significantly worse 12-18 month outcomes, including being significantly less likely to be employed (working) (44% vs. 64%, F=7.02, p=0.009), and having higher rates of emergency visits over the course of the follow-up (35% vs. 19%, F=4.19, p=.042). There was no prospective association between the psychiatric status of the participants and their score on the Asthma Quality of Life Questionnaire, at follow-up, after adjustment for covariates.

Conclusions and clinical implications: Rates of mood or anxiety disorders were disproportionately high (2-4 times greater than rates observed in the general population) in patients presenting for evaluation of OA. Though overall rates of psychiatric disorders and levels of psychological distress were comparable among patients with and without eventual diagnoses of OA or other diagnosable disorders, hypochondriasis was more common among patients not receiving a diagnosable disorder, suggesting that it may underlie a significant proportion of ‘un-diagnosable’ cases of suspected OA. Follow-up results indicate that irrespective of the diagnostic group, patients with a psychiatric disorder at baseline have less favorable 12-18 month outcomes, including being less likely to be employed and having greater use of certain health services (emergency visits). Overall, the results of this study suggest that greater efforts should be made to assess (and treat) psychiatric disorders in this population.