We studied the prevalence of respiratory symptoms and level of lung function among staff working in a large and busy hospital in Iran. We found that hospital workers had significantly higher prevalences of cough, phlegm production, productive cough, and wheezing compared to the reference group of office workers from the same hospital but working in the neighbor building. In addition, among the specific healthcare worker groups, nurses, aid nurses and laboratory workers had increased prevalences of several respiratory symptoms. We also observed significant reductions in the levels of FEV1 and FVC among the subgroups of nurses and other hospital workers in unadjusted models (Table S1). Furthermore, the prevalence of restrictive lung function impairment was higher in the exposed group compared to the reference group.
Healthcare workers are exposed to multiple agents potentially harmful for respiratory health. Disinfection of medical instruments in healthcare is likely to expose workers to substances leading to airway inflammation, especially in work tasks requiring high volumes or concentrations of disinfectants. Use of disinfectants to clean surfaces may also be linked to workers’ exposure to chemical agents that may cause adverse respiratory effects. In our study, local exhaust ventilation was used only in a few work areas.
We also addressed potential interaction between current or former smoking and occupational exposures, i.e., whether smoking modifies effects of such exposures. In our study, current smoking was found to have an independent adverse effect on FEV1/FVC%. Lack of any significant effect on the other lung function parameters could be due to the so-called healthy smoker selection, which means that healthier people are more likely to start smoking and to continue it [17]. In addition, the relatively young average age of this study population (mean 36.3 years, SD 8.25) could explain the rather modest effects on lung function, as the subjects had relatively short duration of smoking. In the main effect models, lung function, apart from FEV1/FVC %-predicted, was statistically significantly reduced in former smokers. The interaction between current smoking and exposure to healthcare chemicals was significant on FEV1/FVC%, suggesting synergism between these two exposures.
Validity Of The Results And Limitations
Study population
We achieved 100% response rate for both the exposed and reference groups, which practically eliminates potential bias that could be related to reduced participation. We compared hospital staff to a reference group of office workers and these two groups were found to have similar demographic and personal characteristics. There were no significant differences with respect to the lifetime smoking between the two groups.
Study Design
This was a cross-sectional study; therefore, it is not possible to elaborate the possibility that workers with respiratory health problems may have been more likely to have left the work compared with workers who remain healthy [18]. This type of selection would lead to underestimation of the relations of interest.
Outcome And Exposure Assessment
Occurrence of respiratory symptoms was assessed with the same questionnaire in a similar way among the occupational subgroups of the hospital staff and that of the control group of office workers. Also, the spirometry measurements were conducted according to same protocol for both the healthcare worker and the office worker groups.
Exposure was assessed in this study with two methods: (1) on the basis of the broad job category, i.e. healthcare worker vs. office worker; and (2) on the basis of subcategory based on job titles. Both types of exposed categories were consistently related to respiratory symptoms. Unfortunately, we were not able to directly measure the occupational exposures.
Confounding
We collected information on several potential determinants of the studied outcomes, which were adjusted for as potential confounders in the multivariate models: personal characteristics (sex, age), socioeconomic status (education), and smoking habits. There is evidence that long-term exposure to air pollution reduces lung function and increases occurrence of respiratory symptoms. We recruited participants of both groups from the same hospital area located in Shiraz, Iran, and thus minimized potential confounding role of air pollution exposure.
Synthesis With Previous Knowledge
The most commonly reported exposures among hospital staff in the United States were cleaning products, latex, and poor indoor air quality in general [19]. Some recent studies have shed additional light on the role of cleaning products in hospital environment [9, 10, 20]. In the present study, prevalence of phlegm production was significantly higher in nurses compared to the office workers (i.e. the reference group), which is consistent with a study by Smedbold et al [21] from Sweden. The authors of the Swedish study concluded that poor indoor environment might have affected the nasal mucosa of the nursing personnel causing nasal mucosal swelling.
The high prevalence of respiratory symptoms among hospital staff in our study is consistent with a previous study from United States [19, 22]. In the present study, the most prevalent symptoms among hospital staff were shortness of breath (31.1%) and cough (23.7%(. These prevalences are somewhat higher than reported in other studies conducted in different parts of the world. In our study, poor indoor air quality in general and exposure to detergents and disinfectants [23] are possible explanations underlying the higher prevalence of respiratory symptoms in the hospital staff. In our study, the clinical laboratory workers reported the highest prevalence of respiratory symptoms among the hospital group. This finding is consistent with results of the study by Mirabelli et al [24]. Increased occurrence of symptoms among nurses was also reported in previous studies by Arif et al [23] and Pechter et al [19].
The previous studies have adjusted for smoking but have not explored potential modifying effect by it among healthcare workers. We did not identify any previous study that had investigated potential interaction between occupational exposures and smoking among healthcare workers. In our study, the interaction between current smoking and healthcare work exposure was significant in relation to FEV1/FVC, which suggests synergism between these two exposures, i.e., current smokers seemed to be more susceptible to the adverse effects of the exposures in hospitals.
We assume that the environmental conditions and the workers of the studied teaching hospital in Shiraz, Iran, represent well the situation also in other hospitals in Iran and other countries in the same region and thus, the results are generalizable at least to some extent.