Psychosocial treatments for employees with non-specific and persistent physical symptoms associated with indoor air: A randomised controlled trial with a one-year follow-up.

Objective: Persistent physical symptoms (PPS) associated with indoor air without an adequate pathophysiological- or environmental-related explanation may lead to work disability and decreased health-related quality of life (HRQoL). We attempted to assess the effect of cognitive behavioural therapy (CBT) for PPS and also psychoeducation (PE) on these symptoms involving disability.
Method: The intention-to-treat (ITT) sample included 52 employees recruited from an occupational healthcare service randomised as either controls undergoing treatment as usual (TAU) or TAU enhanced with CBT or PE. The primary outcome was HRQoL measuring the severity of symptoms and restrictions in everyday life caused by them. Secondary outcomes included depressive, anxiety and insomnia symptoms, and intolerance to environmental factors, assessed at baseline and at 3-, 6- and 12-month follow-ups.
Results: At the 12-month follow-up assessment point, no statistically significant differences between treatments emerged following adjustment for gender, age, and HRQoL before the waiting period in the ITT analysis [F(2,46)=2.89, p=.07]. The secondary analysis revealed a significant improvement in HRQoL in the combined intervention group as compared with controls [F(1,47)=5.06, p=.03, g=0.41]. In total, 15% of participants dropped out during follow-up.
Conclusions: The results suggest that CBT for PPS or PE might not have a robust effect on HRQoL in PPS associated with indoor air, but the study did not achieve the planned power. Despite difficulties during the recruitment process, the final dropout rates remained low, and participants positively evaluated CBT, suggesting that it represents an acceptable treatment to them. Trial status This study was registered at the ClinicalTrials.gov registry (NCT02069002).
Competing Interests: Competing interests Data collection was financially supported by the Finnish Work Environment Fund (ref 113076) and the Social Insurance Institution of Finland (Kela; ref. 23/26/2014). KK worked as a part-time medical consultant at Varma Mutual Pension Insurance Company until 30 November 2019. AV works as a part-time medical consultant at OP Insurance Ltd. and worked as a part-time medical consultant at the Social Insurance Institution of Finland (Kela, until 30 November 2018). AV was a substitute member of the medical expert group of the Unemployment Security Appeal Board (TTLK, in accordance with the Unemployment Security Commission Act) until 31 December 2017. MS works as a part-time medical adviser to the Finnish Patient Insurance Centre (in accordance with the Patient Injuries Act). These affiliations (AV, KK and MS) caused no conflicts of interest regarding this manuscript. None of these institutions profits financially or in any other way from this intervention study, from the publication of the methods used, or from the results reported. Neither the authors' institutions nor the funders had any authority over the trial activities or the preparation of the manuscript.
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