Mortality by idiopathic pulmonary fibrosis

EDITORIAL

Mortality by idiopathic pulmonary fibrosis

José Antonio Baddini Martinez (te sbpt)

Ribeirão Preto Medical School – USP - Specialist degree by SBPT

Idiopathic pulmonary fibrosis (IPF) is the most common of the interstitial lung diseases (ILD). In spite of that, its etiology remains unknown and really effective therapeutic options against the disease are still being researched. Another aspect little known as well is the epidemiology of the disease. Although it is more prevalent in men, especially from the fifth to the sixth decade of life, data on the actual incidence, prevalence and mortality are scarce and unreliable. In a study performed in New Mexico, USA, the annual incidence of IPF was estimated as 11/100,000 for men and 7/100,000 for women ⁽¹⁾.

The lack of adequate epidemiological information on IPF occurs worldwide, and cannot be solely attributed to the chronic problems of the Brazilian health system. Different factors contribute to this situation, such as low incidence of the illness, complexity of the methods required for a precise diagnosis, frequent changes of concepts and definitions, as well as the lack of adequate knowledge of several physicians on the subject. In fact, even among the experts and researchers in this area, there are still several unanswered questions regarding idiopathic interstitial pneumonitis, as a whole, and concerning IPF in particular.

Therefore, studies focused on the epidemiological investigation of ILD are rare in Brazil. Recently, Castro et al. ⁽²⁾, using data provided by DATA-SUS, evidenced a pattern of annual increase of mortality by pneumoconiosis from 1979 to 1998. The transition of the ICD (International Classification of Diseases) 9 to ICD 10 influenced the results obtained, leading to an increase of records of deaths by pneumoconiosis. The mortality coefficient calculated for pneumoconiosis in 1998 was 0.18 deaths/100,000 inhabitants.

In the present issue of the Journal of Pneumology, Fortuna et al. ⁽³⁾ make a retrospective analysis of the data provided by the Regional Center of Health Information of the State of Rio Grande do Sul (Brazil) about mortality by IPF between 1970 and 2000 in this State. The authors noticed a significant mortality increase in those years, a fact which had been described to other countries in international journals in the last decade. In addition to that, comparing mortality rates of this study with that of other countries in similar years revealed a low mortality rate in Rio Grande do Sul. For instance, whereas in 1991 the mortality rate from IPF in Rio Grande do Sul was close to 0.4 deaths/100,000 inhabitants, in Australia and England the values obtained were respectively 1.8 and 2.8 deaths/100,000 inhabitants ⁽⁴⁾. Finally, as was likewise observed by Castro et al., the influence of transition of ICD-8 to ICD-9 and of ICD-9 to ICD-10 was evident on the results.

Studies similar to Castro et al. ⁽²⁾ and Fortuna et al. ⁽³⁾ are very welcome and must be encouraged, because they clearly contribute to a better characterization of the ILD situation in the country. However, as reminded by the authors of the latter paper warn, the "limitations inherent to this kind of study" recommend that "the data be interpreted with proper caution".

Coultas and Hughes ⁽⁵⁾ investigated the use of data obtained from death certificates as an index of ILD in the population. The authors studied 385 patients with previous diagnosis of any ILD, of which 134 died. Of the 129 death certificates found in the analysis, ILD was listed as the causa mortis in only 14.7% of the cases. Reference to ILD was listed somewhere in the certificate (causa mortis, primary disease, or other significant conditions) in 45.7% of the deaths. Regarding the cases of lung fibrosis (ICD-9 515 and 516.3), the diagnostic was listed as the causa mortis in 68.5% of the cases, and somewhere in the certificate, in 71.2% of the deaths. The authors concluded that mortality data underestimate the real incidence of ILD, although this problem occurs less with IPF.

Regardless of the deficiencies of the method employed, the studies published point out to a steady increase of the IPF mortality rates in different regions of the world in the last decades ^(4,6,7). Fortuna and colleagues’ data ⁽³⁾ strongly suggest that the same is happening in Brazil. It is extremely difficult to determine how much this phenomenon is influenced by increased disclosure and knowledge of this condition in the medical environment. Nonetheless, it could also be explained by increased incidence or severity of the cases. Since IPF has always been recognized as a poor prognosis disease, mostly non-responsive to therapy, the first possibility above deserves especial consideration. Investigations directed towards identifying risk factors associated to the development of IPF suggest that smoking, viral infections and inhalation of mineral, animal and vegetal dusts play important roles in this process ⁽⁸⁾. Thus, increased incidence of IPF could be related to behavioral changes or still unknown environmental phenomena.

The study developed by Fortuna and co-workers’ ⁽³⁾ also raises other issues: (i) does the inclusion of only cases in which pulmonary fibrosis was recorded as the main cause of death lead to the exclusion of an expressive number of cases in which IPF could be listed as the primary disease? (ii) what is the level of accuracy and detail that we, the physicians, use filling death certificates of chronic lung disease patients? (iii) is the low mortality rate by IPF in this study, when compared to other countries, due to the low incidence of the disease or to the lack of adequate diagnoses in our environment? (iv) is the current ICD-10 really adequate to portray the complexities related to ILD different diagnoses?

Thus, it is clear that the IPF epidemiology in general, and IPF in particular, is an obscure issue difficult to investigate. Studies such as Castro and colleagues’ ⁽²⁾ and Fortuna and co-workers’ ⁽³⁾ must be encouraged, because they are like small flames that light up the path to be followed.

References

1. Coultas DB, Zumwalt RE, Black WC, Sobonya RE. The epidemiology of interstitial lung diseases. Am J Respir Crit Care Med 1994;150:967-72.

2. Castro HA, Vicentin G, Pereira KCX. Mortalidade por pneumoconioses nas macro-regiões do Brasil no período de 1979-1998. J Pneumol 2003; 29:82-8.

3. Fortuna FP, Perin C, Cunha L, Rubin AS. Mortalidade por fibrose pulmonar idiopática no Rio Grande do Sul. J Pneumol 2003;29:121-4.

4. Hubbard R, Johnston I, Coultas DB, Britton J. Mortality rates from cryptogenic fibrosing alveolitis in seven countries. Thorax 1996;51:711-16.

5. Coultas DB, Hughes MP. Accuracy of mortality data for interstitial lung disease in New Mexico, USA. Thorax 1996;51:717-20.

6. Johnston I, Britton J, Kinnear W, Logan R. Rising mortality from cryptogenic fibrosing alveolitis. BMJ 1990;301:1017-21.

7. Mannino DM, Etzel RA, Parrish RG. Pulmonary fibrosis deaths in the United States, 1979-1991. An analysis of multiple-cause mortality data. Am J Respir Crit Care Med 1996;153:1548-52.

8. Baumgartner KB, Samet JM, Coultas DB, et al. Occupational and environmental risk factors for idiopathic pulmonary fibrosis: a multicenter case-control study. Am J Epidemiol 2000;152:307-15.

Publication Dates

• Publication in this collection
  24 Sept 2003
• Date of issue
  June 2003