Using big data from health records from four countries to evaluate chronic disease outcomes: a study in 114 364 survivors of myocardial infarction

Abstract

Aims: To assess the international validity of using hospital record data to compare long-term outcomes in heart attack survivors.

Methods and results: We used samples of national, ongoing, unselected record sources to assess three outcomes: cause death; a composite of myocardial infarction (MI), stroke, and all-cause death; and hospitalized bleeding. Patients aged 65 years and older entered the study 1 year following the most recent discharge for acute MI in 2002-11 [n = 54 841 (Sweden), 53 909 (USA), 4653 (England), and 961 (France)]. Across each of the four countries, we found consistent associations with 12 baseline prognostic factors and each of the three outcomes. In each country, we observed high 3-year crude cumulative risks of all-cause death (from 19.6% [England] to 30.2% [USA]); the composite of MI, stroke, or death [from 26.0% (France) to 36.2% (USA)]; and hospitalized bleeding [from 3.1% (France) to 5.3% (USA)]. After adjustments for baseline risk factors, risks were similar across all countries [relative risks (RRs) compared with Sweden not statistically significant], but higher in the USA for all-cause death [RR USA vs. Sweden, 1.14 (95% confidence interval 1.04-1.26)] and hospitalized bleeding [RR USA vs. Sweden, 1.54 (1.21-1.96)].

Conclusion: The validity of using hospital record data is supported by the consistency of estimates across four countries of a high adjusted risk of death, further MI, and stroke in the chronic phase after MI. The possibility that adjusted risks of mortality and bleeding are higher in the USA warrants further study.

Figure 1

Age- and sex-standardized prevalence of co-morbidities and secondary prevention treatments in post- myocardial infarction survivors aged 65 years and older. Estimates correspond to the direct age- and sex-standardized prevalence of co-morbidities in each country using as reference the 2012 World Health Organization world population truncated to age 65 years and older. ACEI, angiotensin-converting enzyme inhibitor; ADP, adenosine diphosphate; ARB, angiotensin receptor blocker; CABG, coronary artery bypass graft; COPD, chronic obstructive pulmonary disease; CVD, cardiovascular disease; MI, myocardial infarction; PAD, peripheral arterial disease; PCI, percutaneous coronary intervention.

Figure 2

Risks of all-cause death in post-myocardial infarction survivors aged 65 years and older followed from 1 year after the index myocardial infarction. Observed (Kaplan–Meier) risks (top left), adjusted risks (top right), and relative risks vs. Sweden (bottom) in post-myocardial infarction survivors from Sweden (n = 54 841), USA (n = 53 909), England (n = 4653), and France (n = 961). CABG, coronary artery bypass graft; CI, confidence interval; KM, Kaplan–Meier; PCI, percutaneous coronary intervention; RR, relative risk.

Figure 3

Risks of the composite of myocardial infarction, stroke, and all-cause death in post-myocardial infarction survivors aged 65 years and older followed from 1 year after the index myocardial infarction. Observed (Kaplan–Meier) risks (top left), adjusted risks (top right), and relative risks vs. Sweden (bottom) in post-myocardial infarction survivors from Sweden (n = 54 841), USA (n = 53 909), England (n = 4653), and France (n = 961). CABG, coronary artery bypass graft; CI, confidence interval; KM, Kaplan–Meier; PCI, percutaneous coronary intervention; RR, relative risk.

Figure 4

Risks of hospitalized bleeding events in post-myocardial infarction survivors aged 65 years and older followed from 1 year after the index myocardial infarction. Observed (Kaplan–Meier) risks (top left), adjusted risks (top right), and relative risks (bottom) for hospitalized bleeding events among post-myocardial infarction survivors from Sweden (n = 54 841), USA (n = 53 909), England (n = 4653), and France (n = 961). CABG, coronary artery bypass graft; CI, confidence interval; KM, Kaplan–Meier; PCI, percutaneous coronary intervention; RR, relative risk.

Figure 5

Age- and sex-adjusted hazard ratios (95% confidence interval) for the association of age, sex, and medical history with the composite of myocardial infarction, stroke, and all-cause death among post-myocardial infarction survivors from Sweden (n = 54 841), USA (n = 53 909), England (n = 4653), and France^a (n = 961). ^aIncidence of PAD in the French study was <0.5%; hence, it was not possible to obtain estimates of association with outcomes. CI, confidence interval; COPD, chronic obstructive pulmonary disease; HR, hazard ratio; MI, myocardial infarction; PAD, peripheral arterial disease.