This is a population-based cohort study that used electronic patient records and aimed to investigate the risk of incident ischaemic heart disease (IHD) and myocardial infarction (MI) in patients with interstitial lung disease (ILD), compared with those without, using linked data from primary and secondary care. IHD is the second most common cause of death in patients with IPF, after IPF itself. The underlying pathogenesis of ILD and IHD share a number of pathophysiological mechanisms including oxidative stress, vascular endothelial injury and release of pro-inflammatory cytokines associated with a hypercoagulable state and formation of microthrombi.
In order to determine that, 11 688 ILD patients were included (mean follow-up: 3.8 years). ILD patients were divided in two major categories; those with pulmonary fibrosis (PF) and those with pulmonary sarcoidosis (PS). Each incident case was matched (by age, sex, registered general practice and available follow-up time) to five controls without ILD or IHD/MI (56 884 controls, mean follow-up: 4.0 years). Rates of incident MI and IHD were estimated. HRs were modelled using multivariable Cox proportional hazards regression accounting for potential confounders; body mass index (BMI), smoking status and alcohol consumption, hypertension, hyperlipidaemia, diabetes, chronic kidney disease, prescription for cardiovascular drugs, reported family history of cardiovascular disease and socioeconomic status.
Both men and women with PF were at increased risk of IHD and MI compared with controls. In particular, PF patients have a 2–3 fold greater incidence of acute myocardial infarction (AMI) and IHD in younger age groups compared with PS and controls. Women with PF were at greatest risk of MI (approximately 80% excess risk) and greater than their male counterparts, while men with PF were at greatest risk of IHD (also approximately 80% excess risk). Risk of both IHD and MI peaked between ages 60 years and 69 years. The PS group was not found, overall, at increased risk of MI or IHD, with the exception of the youngest age group (<50 years) which exhibited an increased risk of MI.
This is an interesting epidemiologic study that included a large number of patients compared to the previous ones and reported an independent, increased risk of MI and IHD in patients with pulmonary fibrosis after adjustment for the established cardiovascular risk factors. Moreover, a stratification of the risk by age and gender was investigated too.
As we have a matched sample and not two randomly selected subjects, bias that have been induced by matching cannot be excluded. Additionally, the sample was collected between 1998 and 2017 and the term PF may not be identical to IPF, so inclusion of patients with other fibrosing diseases is possible. Finally, the finding of increased risk of MI in the youngest age group (<50 years) with PS cannot be explained adequately and needs further investigation. Nevertheless, these results suggest that clinicians should include targeted assessment of cardiovascular risk in patients with PF.