Asthma is a chronic inflammatory respiratory disease, and one of the most frequent chronic diseases in the world, with recent estimates ranging from 225 to 334 million.1

Estimates of the economic burden of asthma are unavailable for most countries and are difficult to quantify. Furthermore, studies in different parts of the world present highly variable estimates.

Direct costs are related to healthcare system usage, such as scheduled and unscheduled appointments, hospitalisations or emergency room visits, pharmacological treatment, and diagnostic tests. Indirect costs include productivity loss, such as work absenteeism, as well as transportation costs.1 A systematic review published in 2012 reported that direct costs outweigh indirect costs.2 Importantly, direct costs have been found to be reduced by better clinical control of asthma, which should be a feasible target to decrease this financial burden.1,3

In Portugal, recent estimates put asthma prevalence at 6.8% (95%CI: 6.0–7.7)4 but its economic burden is still unknown, due to a lack of cost-of-illness studies. These are needed to support decision-makers in defining priorities for health policies and programmes. Especially with the political and social pressure related to the continuous growth of healthcare-related costs, which in 2010 already amounted to 9.9% of the Portuguese gross domestic product.

Therefore, the aim of this paper is to estimate the total cost imposed on the Portuguese society by asthma in adults, as well as the extent to which direct and indirect costs are influenced by the level of asthma control.

A nationwide, prevalence-based cost-of-illness study with a societal perspective was conducted. This study was reviewed and approved by the Ethics Committee of Centro Hospitalar de São João, Porto, Portugal. Informed consent was obtained.

This study included 309 participants from the Portuguese National Asthma Survey (INAsma study), which was a nationwide survey, from the general population, done through telephone interview to individuals living in Portugal in 2010. The study methodology has been previously described.4,5 Moreover, data regarding the price of healthcare services, diagnostic tests, medication, absenteeism, and transportation was collected from different resources and databases as described below.

Participant characteristics and simple quantification of healthcare system usage, medication regimes, available information on diagnostic tests and absenteeism are summarised in Table 1. Participants living in 125 municipalities spread throughout the country, out of the existing 308, were assessed.

Estimates of mean and total yearly costs are presented in Table 2. On average, each adult costs 708.16€ (95%CI: 594.62–839.30), with direct costs representing 93% (658.46€; 95%CI: 548.99–791.29) and indirect costs representing the remaining 7% (49.70€; 95%CI: 32.08–71.56). This amounts to a grand total of 386,197,211.25€ (95%CI: 324,279,674.31–457,716,500.18), with direct costs being 359,093,559.82€ (95%CI: 299,391,930.03–431,533,081.07) and indirect costs being 27,103,651.43€ (95%CI: 17,496,371.57–39,025,309.60).

The direct cost amounts to 2.04% of the total Portuguese healthcare expense for 2010. Acute care usage and treatment were the major cost drivers, with 30.7% and 37.4%, respectively.

Table 3 shows that patients classified according to asthma control have statistically significant differences in total, direct, and indirect costs. Regarding direct costs, acute care usage and treatment are significantly different, while scheduled medical visits and diagnostic tests are not. As for indirect costs, transportation has a significant difference, whereas absenteeism does not. While statistical significance was absent for some specific subdomains, uncontrolled patients were associated with a higher expense in every included domain except for diagnostic tests. In controlled patients, mean total cost was 425.44€, while uncontrolled patients had a mean total cost of 894.86€. Asthma control information was missing for 8 patients, so they were not included in this analysis.

Multivariate deterministic sensitivity analysis, shown in Table 4, shows predicted best- and worst-case scenarios for each domain. Mean total yearly cost per patient is expected to vary between 546.95€ and 840.08€, corresponding to grand totals of 255,894,084.77€ and 523,248,043.91€, respectively.

We conducted a detailed cost-of-illness analysis of asthma in Portuguese adults, with a prevalence-based, societal perspective, that allowed a broad economic analysis of the disease.

Adult asthma costs over 380M€ per year, with a mean annual cost per patient of over 700€ which are spread between the patients, the Portuguese state, and health insurance companies, depending on the healthcare services the patients use. This is in line with the cost estimates of 929.35€ per child calculated using the same methods, and also from INAsma,6 including a mean of 129.24€ of state subsidies not given to adults. This would put total costs at 547,607,218.86€ (mean 761.58€ per patient, 3% of the total healthcare expense in 2010). Our mean values are close to previous estimates for countries such as Canada and Australia (766$ and 779$, respectively), with similar state-funded healthcare, and to the value from an institutional study in the U.S.A. (727$).2,7,8 However, other studies in countries within the European Union, such as Spain or Italy, present much higher figures (3970$ and 2038$, respectively – converted prices), surprisingly.2,9,10 Nevertheless, most of these studies are institutional, as there is a lack of nationwide studies, and variability is high, with other estimates in the US going upwards of 4000$.2 As far as total expenditure is concerned, a study in Spain shows a smaller relative expense (percentage of total healthcare cost) of 1–2% in asthma, but the smaller prevalence (4.7%) may explain this difference, despite the aforementioned higher cost per patient related to the origin of the samples.11

In most studies, direct costs outweigh indirect costs, but not by such a wide margin as we observed. In some studies, however, indirect costs make up the majority of total costs.2,9,10,12–14 This difference in indirect costs may be attributed to an underestimation in our study, due to a lack of data regarding loss of productivity, specifically on presenteeism assessment,15,16 and of quantification of the costs of comorbidity, early retirement, and life expectancy loss.9

As expected,1,3,9 we observed that uncontrolled patients pose a much higher annual economic burden than those whose asthma is controlled, with a 2.1-times increase in mean total cost. This is most significant in the “acute care usage” cost domain. However, both domains of asthma-specific treatment costs are significantly higher in uncontrolled patients as well, suggesting that these patients are on more costly treatment regimes, yet still have a greater need for relief medication. This favours the view that improving control can be an effective way of decreasing costs.

The study's main limitations regarding methodology and study design are the assumptions that had to be made using a clinical consensus approach to compensate for the lack of information in some parameters, namely: (1) diagnostic tests (skin prick tests, chest x-rays, and blood workouts); (2) to which specific hospital catchment area some participants belonged to; (3) how much relief medication they used during an exacerbation; and (4) other medications (allergen-specific immunotherapy and Influenza vaccination). This stems from the fact that data was obtained from surveys not specifically developed for cost research.

Moreover, this study has limitations regarding indirect costs as stated above. Therefore, future investigation should use data collection methods specifically devised for assessing costs, with sufficient data for all domains. Nevertheless, this is the first study of this type in Portugal for asthma, and this study should prompt further investigation into the economic burden of such a prevalent disease. From a social perspective, since the Portuguese healthcare system is mostly tax-funded, patients are provided with free healthcare bar standard moderation fees, and the state provides co-payments for medication, there is a significant interest in reducing treatment costs and mitigating the need for acute hospital care.

Extrapolation of these results from 2010 to a current-day scenario is limited by changes in asthma care. New treatments, especially biological agents for severe asthma, may increase costs, while better asthma control may decrease them.17 New studies on asthma burden, building on the knowledge provided by INAsma, the Portuguese National Asthma Survey (2010) should be done in the near future, updating these results.

In conclusion, adult asthma poses a significant economic burden to the Portuguese healthcare system, having accounted for over 2% of the total healthcare expenditure in Portugal in 2010 (3% if children and adults are included). Importantly, a considerable portion of this burden might be eased by improving asthma control in patients, as uncontrolled patients’ costs are more than double than those of controlled asthma patients.

The authors have no conflicts of interest to declare.