Work-related asthma (WRT)1–3 is a term that covers all types of asthma associated with the occupational environment. It includes both occupational asthma (OA), officially classified as work-related disease that is caused by exposure and conditions fully attributable to the working environment,1,4,5 and work-exacerbated asthma (WEA), which occurs when pre-existing or concurrent asthma is aggravated by workplace exposure.6

Epidemiological and clinical evidence suggests that asthma may be induced by exposure to multiple inhaled agents in the working environment – over 400, according to current estimations.2,7–9

OA is the most common occupational respiratory disease in industrialized countries.10,11 Although most studies12,13 report a WRA prevalence of between 5% and 25%, more recent reviews14,15 estimate that the mean risk attributable to working conditions is around 15%–16%. Moreover, the mean prevalence of WEA among adults with asthma is estimated to be 21%.6 Since asthma affects between 5% and 10% of adults in Europe (the estimated prevalence in Spain is 5%),16,17 WRA is a serious public health problem with significant socioeconomic implications.13,18,19

One major occupational health problem in Spain is that OA is frequently not detected and diagnosed as such in the specialized departments of the occupational healthcare system, consisting of company healthcare provisions and the MATEPSS (the work-related accidents and occupational diseases insurance section of the Spanish social security system). Instead it is diagnosed and treated as a common non-work-related disease within the primary health care (PHC) system.20,21 This results in either a delay in diagnosis of WRA, or a complete failure to diagnosis the condition as work-related. This situation causes serious harm: affected workers continue to be exposed to the causative agent and their condition deteriorates, chronicity sets in and they lose their capacity for work. Other workers, too, may suffer from the same exposure while performing similar tasks, since the company fails to implement preventive measures for avoiding new cases. To minimize both delay in diagnosis and long-term decline due to WRA, primary care physicians, when diagnosing asthma in adults, must always consider the possibility that the disease may be work-related.22

Although some estimations of the healthcare costs of work-related asthma have been made,18 no studies have been conducted in our setting that quantify, based on the number of patients seen, the true burden of this shift of patients and costs toward PHC. We know that the problem exists but we are unaware of its real magnitude.

The purpose of this study was to estimate the prevalence of WRA (both OA and WEA) in patients diagnosed with asthma, and to determine the real impact on PHC caused by underdiagnosis and failure to refer cases of OA to occupational insurance companies. We aimed to determine the prevalence of patients with OA treated in PHC (who should have been seen in the MATEPSS), and to calculate the burden in terms of both costs and workload. This knowledge is essential for adopting corrective measures and achieving the final objective: to improve the healthcare and occupational prognosis of patients with OA and WEA, and to improve risk prevention in the workplace, thereby reducing the incidence of new cases.

This was a descriptive, cross-sectional, multicenter study, conducted in the territorial framework of a healthcare district with 16 PHC teams and a population distributed among semi-rural and urban areas. According to the 2009 municipal register, the total population of the area is 384718 inhabitants, all of whom are entitled to public healthcare and have been assigned to a PHC center, according to their place of residence.

At total of 2505 patients with a diagnosis of asthma were identified from a population of 102131 subjects aged between 16 and 64 years. The recorded asthma prevalence in this study population was 2.5%.

The medical records of 822 asthma patients were reviewed to include a total of 368 in the study (Fig. 1). Table 1 shows the characteristics of these patients, according to their asthma diagnosis. A total of 67 were diagnosed with OA, corresponding to a prevalence of 18.2%, with respect to the total number of study patients aged between 16 and 64 years. Prevalence was greater in men than in women (P=.046). If the 54 patients with WEA are included, the overall prevalence of work-related asthma was 32.9%. Only 2 of the 368 cases reviewed had been referred to occupational insurance facilities due to clearly suspected OA.

Fig. 1.

Patient selection flow-chart.

(0.15MB).

Patients with OA were significantly older than the other asthma patients (P<.001), and were also significantly older at onset of symptoms (P<.001) (Table 1). Prevalence of OA in unemployed subjects or those considered to have permanent incapacity was higher than in asthma patients in active employment (P=.013). The prevalence of OA in patients in occupational groups B or C at onset of symptoms was also higher than in group A subjects (P<.001) (Table 1). After performing the multivariate analysis, the characteristics that were eventually significantly associated with a higher prevalence of OA were symptom onset at an older age, and employment in group B or C occupations at the time of symptom onset.

Table 2 shows the use of resources generated over 1 year by study patients, according to their asthma diagnosis. Patients with work-related asthma (OA and WEA) took more sick leave for common illness granted by doctors from the PHC system than those with CA (P<.001). In 1 year, patients with OA made a mean of 3.1 visits to their PHC physician, and used 14.8 containers of inhaled drugs (P=.048), at a cost of €351.16. These figures were higher for OA patients than for those with CA and WEA, but the differences were not statistically significant. With regard to hospital admissions and visits to the emergency department due to asthma, only 2 patients with OA were hospitalized during 2009.

Of the 67 patients with OA, 11 (16.4%) had been seen on at least 1 occasion for asthma in the MATEPSS, and of these, 5 had been seen on 2 or more occasions in their occupational insurance company. The remaining patients were always treated in the PHC system. Furthermore, 62 (16.8%) patients did not require inhaled medication (12 with OA [17.9% of OA patients], 8 with WEA [14.8% of those with WEA] and 42 with CA [17.0% of those with CA]), although these differences were not statistically significant.

The results suggest that in 32.9% of asthma patients treated in the PHC system, there is a relationship between their disease and their working environment. In 18.2%, the asthma was caused by conditions in the workplace itself, while in 14.7%, it was exacerbated in the workplace.

Variability in study methods and definitions mean that the prevalence of WRA is not well defined in general, and our results are comparable to those of other reviews, both European and American, that reported wide ranges of between 5% and 25%.12–15 The significance of this study is that it was conducted in the primary care setting of the public health service. Classification of patients into 3 categories (OA, WEA and CA) by a specialist physician using data collected in a questionnaire is not exempt from problems, but we believe that it is a method fit for the purposes of this study. This methodology may underestimate cases of OA, and may not be helpful in assessing the prevalence of WRA.25 Nonetheless, additional testing (such as sensitization or specific bronchial hyperreactivity testing), while necessary in individual diagnosis due to the medical and/or legal implications of the disease, does not provide any relevant supplementary information26 in population studies.

The low prevalence (2.5%) of asthma observed in our study is because of under-reporting of the disease, both due to the problem of under-reporting itself, and because the study was performed in the early years after switching from paper medical records to the EMR, and transfer of diagnoses was not automatic.

While the total number of women with asthma is higher than that of men, a greater percentage of men have OA. This discrepancy cannot be explained simply by differences in exposure to allergens.27,28 Some studies have reported a higher risk of OA in women employed as domestic cleaners.29 This parameter is not so discernible in our study, probably because cleaners are unofficially employed and so do not have their own social security number, a requisite for inclusion in this study. As asthma in this population cannot be legally classified as OA, many women are diagnosed as having CA when they really have OA.

Patients with OA are older than those with WEA and CA. In OA, asthma is triggered by working conditions, and a period of sensitization is needed before the disease manifests.30 In contrast, CA and WEA are triggered by factors encountered before the work-related exposure. Onset of symptoms in patients with WEA occurs at a very young age, suggesting that aggravation of childhood or pre-existing asthma due to work exposure occurs rapidly. A total of 27% of patients whose asthma was diagnosed after the age of 30 years were diagnosed with OA. This would suggest that when asthma is diagnosed in adults, the possibility that the disease may be work-related must be explored.

With regard to the patients’ country of origin, it is interesting to note that immigrants are not overrepresented among cases of OA or, especially, WEA, despite them having jobs that might involve a greater risk of exposure to more allergenic substances with fewer protective measures. However, conclusions cannot be drawn, due to the small numbers in our sample. No differences were observed between smoking habit and the different types of asthma.

Unemployment and incapacity for work in patients with OA are significantly higher than in other groups. It seems very likely that the disease affects sufferers’ possibilities of finding work and being declared with permanent incapacity for work by Employment Institute inspectors. This fact shows how the course of asthma can be particularly incapacitating for OA patients. Moreover, if the patient's disease is not recognized as occupational, their financial situation can be severely affected. Patients with OA and WEA have more episodes of temporary incapacity for work due to asthma (only 4.5% of these were granted by the occupational insurance agencies) than patients with CA. This is another indication of the poor progress of WRA patients caused by continuous exposure to the allergens that trigger or exacerbate their asthma.

Data on medication use show that, although the proportion of CA and OA patients who do not need asthma medication (estimated from pharmacy use) is similar, the number of containers used by OA subjects is significantly higher. Expenditure on medication use by patients with OA is higher than in those with CA. The number of visits to PHC is also higher in OA, although the difference is not statistically significant. Curiously, the behavior of WEA subjects is similar to that of those with CA.

In short, OA patients use more healthcare resources than other patients with asthma. In fact, according to legal provisions (Legislative Royal Decree 1/1994, 20 June 1994, approving the Consolidated General Social Security Act), patients with OA should be referred to and treated by the occupational healthcare system, which is not the case.

This study underscores the high prevalence of WRA treated in PHC centers. The healthcare burden is high, and treatment in the PHC system does not contribute to any improvement in the health of these patients, since the working conditions that trigger or aggravate their disease remain unchanged.

It must also be emphasized that OA is rarely suspected in the PHC system: the possibility of OA was considered in only 2 of the 368 cases reviewed. These findings are consistent with those from other studies.31 OA should be considered more often as a diagnosis in all adults with symptoms indicative of asthma. Information on current and previous working environments should be included in the patient's medical record.

Our proposal, also suggested in other European studies,32,33 is to implement protocols encouraging the suspicion and detection of WRA in primary care, as well as better detection and follow-up by occupational insurance agencies. This would increase the diagnostic rate and improve the disease course and prognosis of patients with OA, and appropriate preventive measures could be introduced to help reduce the incidence of new cases. We must all work toward greater communication and collaboration between the public healthcare system and the occupational healthcare system (MATEPSS), in order to improve the diagnosis, treatment, and outcome of patients with this disease.

This study was approved by the Clinical Research Ethics Committee of the Instituto de Investigación en Atención Primaria (IDIAP) Jordi Gol (Barcelona).

The investigators complied with current Good Clinical Practice guidelines and respected the requirements of the Declaration of Helsinki (1975). Accordingly, a 7-digit code was used to anonymize the patients: the first 2 digits identified the study site, the next 2 digits identified the medic who made the evaluation, and the final 3 digits reflected the order of inclusion of the patient in the study. During the first visit, the healthcare professional provided the patient with an information sheet and requested their voluntary participation, and the informed consent form was signed.

This study was made possible by a grant from the Instituto de Investigación en Atención Primaria (IDIAP) Jordi Gol (Barcelona), conceded in 2008.

The authors state that they had no conflict of interests.