Comorbidity in real-world pulmonary fibrosis runs well above the trial cohorts

Design

systematic review and meta-analysis of 251 observational studies, searched to August 2024

Population

606,398 adults with idiopathic pulmonary fibrosis in clinical cohorts

Primary outcome

pooled comorbidity prevalence, with outcome associations synthesised narratively

Effect

hypertension 39% (34-44), dyslipidaemia 30% (20-38), reflux 27% (23-31), diabetes 21% (19-23); lung cancer the only comorbidity consistently linked to mortality

Two hundred and fifty-one observational studies, each of at least 100 adults with idiopathic pulmonary fibrosis, were pooled - 606,398 patients - to estimate how often each comorbidity occurs in clinically encountered rather than trial-enrolled populations.

Hypertension was present in 39% (95% CI 34 to 44), dyslipidaemia 30% (20 to 38), gastro-oesophageal reflux 27% (23 to 31), hiatus hernia 20% (9 to 33), overweight or obesity 22% (18 to 27), diabetes 21% (19 to 23), ischaemic heart disease 20% (17 to 23) and heart failure 15% (13 to 18). Most exceed the rates reported in IPF trial cohorts. Relationships between comorbidity and quality of life or disease progression were rarely studied and could only be synthesised narratively. Lung cancer was the only comorbidity consistently associated with both short and long-term mortality.

The practical consequence is about what the trial evidence covers. Antifibrotic trials recruited a healthier population than the one in clinic, so tolerability, drug interactions and the competing burden of cardiovascular disease are less well characterised than efficacy. The reflux figure is the other one worth holding: at 27% pooled, and higher in some cohorts, it is common enough that the question of whether to treat it is a routine one, and the evidence that treating it changes the lung disease remains absent.

• Screen for and manage cardiovascular risk actively - hypertension and dyslipidaemia were the two commonest comorbidities
• Ask about reflux symptoms specifically; the prevalence is high and patients often do not volunteer them
• Maintain lung cancer surveillance awareness - it was the only comorbidity consistently linked to mortality here
• Expect more drug interactions and tolerability problems than the antifibrotic trials suggest
• Do not attribute all weight loss to the antifibrotic without reviewing the alternatives

Why it matters

It shows the patient in front of you carries more competing disease than the population the antifibrotic evidence was generated in.

Don't overread it

A prevalence synthesis of observational cohorts - it does not show that any comorbidity drives progression or that treating one alters the fibrosis.

The statistics, in plain English

Some of these pooled estimates are tight and usable - diabetes at 19 to 23% across 251 studies - and others are not: hiatus hernia ran from 9 to 33%, dyslipidaemia from 20 to 38%, meaning the studies disagreed enough that the single number should not be quoted. Prevalence also tells you nothing about direction: whether these conditions worsen fibrosis, share risk factors with it, or simply accumulate with age in the same patients is not addressed here, and the review says associations with outcomes were too rarely studied to pool.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.