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Idiopathic pulmonary fibrosis in US Medicare beneficiaries aged 65 years and older: incidence, prevalence, and survival, 2001–11

https://doi.org/10.1016/S2213-2600(14)70101-8Get rights and content

Summary

Background

Published data for the epidemiology of idiopathic pulmonary fibrosis in the USA are scarce. We sought to estimate the incidence, prevalence, and mortality risk of idiopathic pulmonary fibrosis among US Medicare beneficiaries.

Methods

We used administrative claims from a 5% random sample of Medicare beneficiaries (aged 65 years and older) from the years 2000–11 as a data source. Idiopathic pulmonary fibrosis was defined by International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes. We estimated annual incidence and cumulative prevalence of idiopathic pulmonary fibrosis, median survival time of patients, and potential risk factors for diagnosis of idiopathic pulmonary fibrosis and death between 2001 and 2011. We also estimated incidence and prevalence using more restrictive algorithms for diagnosis.

Findings

The annual incidence of idiopathic pulmonary fibrosis in the Medicare population remained stable between 2001 and 2011, with an overall estimate of 93·7 cases per 100 000 person-years (95% CI 91·9–95·4) across the study period. The annual cumulative prevalence increased steadily from 202·2 cases per 100 000 people in 2001 to 494·5 cases per 100 000 people in 2011. Among newly diagnosed patients with Medicare (mean age 79·4 years [SD 7·2], 54% female, 91% white), the median survival time was 3·8 years (95% CI 3·5–3·8). Older age and male sex were associated with a higher incidence of disease and shorter survival time after diagnosis. Mortality risk was lower in patients diagnosed in more recent years (median survival time 3·3 years [95% CI 3·0–3·8] in 2001 vs 4·0 years [3·8–4·5] in 2007).

Interpretation

The incidence and prevalence of idiopathic pulmonary fibrosis in people aged 65 years and older in the USA are substantially higher than previously reported, and prevalence is increasing annually, even in the subgroups based on more restrictive algorithms for diagnosis. Patients with idiopathic pulmonary fibrosis aged 65 years and older were living longer in 2011 than they were 10 years before, which could partly account for the steady increase in prevalence.

Funding

Biogen Idec.

Introduction

Idiopathic pulmonary fibrosis, a specific form of chronic, progressive fibrosing interstitial pneumonia of unknown cause, is a highly morbid disorder.1, 2, 3 It has an unpredictable clinical course, but eventually causes decline in pulmonary function and death from respiratory failure or complicating comorbidity.4, 5 Median survival is estimated to be 2–5 years from the time of diagnosis.6, 7, 8, 9, 10 No well established treatments exist for this disease.2

Published data about the epidemiology of idiopathic pulmonary fibrosis in the USA is scarce and outdated, especially data generated from nationally representative cohorts.11 Data from one population-based registry in Bernalillo County, NM, from 1988 to 1990 showed the prevalence of idiopathic pulmonary fibrosis to be 20·2 per 100 000 people for men and 14·3 per 100 000 people for women, and the incidence to be 10·7 per 100 000 person-years for men and 7·4 per 100 000 person-years for women.12 In another regional study in Olmsted County, MN, based on data from 1997 to 2005, estimates of prevalence ranged from 27·9 to 63·0 per 100 000 people and estimates of incidence ranged from 8·8 to 17·3 per 100 000 person-years.10 The only national study13 reported so far (based on data from a private insurance claims database for 1996 to 2000) produced estimates of prevalence that ranged from 14·0 to 42·7 per 100 000 people and estimates of incidence that ranged from 6·8 to 16·3 per 100 000 person-years, and showed an increase in incidence and prevalence with advancing age. All of these studies included patients diagnosed with idiopathic pulmonary fibrosis before the definition was revised in 2000,14 and none of them provided data for mortality risk.

The aim of this study was to describe the epidemiology of idiopathic pulmonary fibrosis (including prevalence, incidence, and mortality) using a large, contemporary, and comprehensive database of people aged 65 years and older in the USA.

Section snippets

Data Source

We used a 5% random sample of Medicare beneficiaries, which is representative of the overall population covered by the Centers for Medicare & Medicaid Services, the largest insurer of people aged 65 years and older. We analysed claims data for the years 2000 to 2011, inclusive. Data included information about year of birth, sex, race or ethnic origin, date of death (if deceased), reasons for Medicare entitlement, and Medicare Advantage Plan (health maintenance organisation) enrolment.

Medicare

Results

The 2000–11 Medicare 5% dataset contained more than 3·7 million beneficiaries, of whom 2 871 436 were eligible for Medicare because of age (figure 1). 23 315 patients had a diagnosis code of 516.3. After exclusion of patients with other codes for interstitial lung disease (apart from for 515), there were 15 259 patients with prevalent idiopathic pulmonary fibrosis, including 12 066 patients with incident disease (primary cohort). Table 1 lists the demographic characteristics of the patients

Discussion

In this study we used a large, nationally representative US database of patients aged 65 years and older to investigate the incidence, prevalence, demographic characteristics, and mortality risk of idiopathic pulmonary fibrosis. This study builds on the previous population-based study by Raghu and colleagues,13 as well as testing different algorithms and providing mortality data (panel). Additionally, this study also contributes to the scientific literature11, 16 by providing data specifically

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