Chest
Volume 147, Issue 1, January 2015, Pages 150-156
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Original Research: Diffuse Lung Disease
Risk Factors for Cardiovascular Disease in People With Idiopathic Pulmonary Fibrosis

https://doi.org/10.1378/chest.14-0041Get rights and content

OBJECTIVE

People with idiopathic pulmonary fibrosis (IPF) have been shown to be at an increased risk for cardiovascular (CV) disease, but reasons for this are unknown. The aim of this study was to compare the prevalence of common CV risk factors in people with IPF and the general population and establish the incidence of ischemic heart disease (IHD) and stroke after the diagnosis of IPF, controlling for these risk factors.

METHODS

We used data from a large, UK primary care database to identify incident cases of IPF and matched general-population control subjects. We compared the prevalence of risk factors for CV disease and prescription of CV medications in people with IPF (before diagnosis) with control subjects from the general population and assessed the incidence of IHD and stroke in people with IPF (after diagnosis) compared with control subjects.

RESULTS

We identified 3,211 cases of IPF and 12,307 control subjects. Patients with IPF were more likely to have a record of hypertension (OR, 1.31; 95% CI, 1.19-1.44), and diabetes (OR, 1.20; 95% CI, 1.07-1.34) compared with control subjects; they were also more likely to have been prescribed several CV drugs. The rate of first-time IHD events was more than twice as high in patients than control subjects (rate ratio, 2.32; 95% CI, 1.85-2.93; P < .001), but the incidence of stroke was only marginally higher (P = .09). Rate ratios for IHD and stroke were not altered substantially after adjusting for CV risk factors.

CONCLUSIONS

Several CV risk factors were more prevalent in people with IPF; however, this did not account for the increased rate of IHD in this group of patients.

Section snippets

Data Source

We used The Health Improvement Network (THIN), a UK longitudinal database of electronic primary care records containing information recorded in routine clinical care, from face-to-face consultations, and following communication from secondary care.11 Anonymized patient-level data include demographic information, medical diagnoses (coded using Read codes), and prescriptions. The version of THIN used for this study included information from 511 practices entered up to September 2011.

Study Population

We identified

Exposures and Outcomes

We extracted data on diagnoses of IHD, ischemic and hemorrhagic stroke, hypertension, diabetes, hypercholesterolemia, and prescriptions for CV and diabetic medications, as well as smoking habit (current smoker, exsmoker, never smoker) using the data recorded closest to the index date, and BMI.

Statistical Analysis

We conducted a case-control study to compare the prevalence of risk factors for CVD and prescription of CV medications in people with IPF with control subjects from the general population. Conditional logistic regression was used to compare the odds of these exposures, prior to the index date, in patients and control subjects. We looked for evidence of effect modification by age and sex.

We performed a cohort study to investigate whether incidence of IHD or stroke was increased after diagnosis

Results

There were 3,211 incident cases of IPF and 12,307 matched, general-population control subjects. Most of the patients were men (63.9%), and mean age at diagnosis was 75.7 years (SD, 9.8). Both patients and control subjects had a median of 9.8 years (interquartile range [IQR], 5.6-13.7) of computerized records prior to the index date.

Case-Control Study

Patients with IPF were 31% more likely to have a record of hypertension (OR, 1.31; 95% CI, 1.19-1.44; P < .001), and 20% more likely to have a record of diabetes mellitus prior to receiving a diagnosis of IPF compared with control subjects (OR, 1.20; 95% CI, 1.07-1.34; P < .001). We also found that patients were more than twice as likely to be exsmokers before the diagnosis of IPF was made compared with control subjects (Table 1). Patients with IPF were more likely to have been prescribed

Cohort Study

Median follow-up time after the index date was 1.7 years (IQR, 0.6-3.6 years) in patients with IPF and 3.3 years (IQR, 1.5-5.8 years) for control subjects. During this time, 135 patients and 474 control subjects had a first-time IHD event. The rate of first-time IHD events was more than two times higher in patients with IPF compared with control subjects (RR, 2.32; 95% CI, 1.85-2.93; P < .001) (Fig 1, Table 3). The incidence rate of stroke during the follow-up period was 11.3 per 1,000

Discussion

In this large population-based study, we found that people with IPF were more likely to have a recorded diagnosis of hypertension and diabetes mellitus before the diagnosis of IPF was made compared with the general population. People with IPF were also more likely to be prescribed antianginals, antiplatelets, and lipid-lowering medication compared with general-population control subjects. Individuals with IPF had twice the rate of first-time IHD events after their diagnosis compared with the

Acknowledgments

Author contributions: V. N. had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. W. D. served as principal author. R. B. H. and V. N. contributed to the conception and design of the study; W. D, H. A. P., R. B. H., and V. N. contributed to the data analysis and interpretation; W. D. and V. N. contributed to drafting the manuscript; H. A. P. and R. B. H. contributed to revision of the manuscript; and W. D.,

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    FUNDING/SUPPORT: Dr Hubbard is the British Lung Foundation/GlaxoSmithKline professor of respiratory epidemiology. Dr Powell is funded by the National Institute for Health Research (NIHR) through the Nottingham Respiratory Research Unit. Dr Navaratnam is an NIHR-funded Academic Clinical Fellow.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.

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