Trends in diagnostic patterns and mortality in emergency ambulance service patients in 2007-2014: a population-based cohort study from the North Denmark Region

Abstract

Objective: Demand for ambulances is growing. Nevertheless, knowledge is limited regarding diagnoses and outcomes in patients receiving emergency ambulances. This study aims to examine time trends in diagnoses and mortality among patients transported with emergency ambulance to hospital.

Design: Population-based cohort study with linkage of Danish national registries.

Setting: The North Denmark Region in 2007-2014.

Participants: Cohort of 148 757 patients transported to hospital by ambulance after calling emergency services.

Main outcome measures: The number of emergency ambulance service patients, distribution of their age, sex, hospital diagnoses, comorbidity, and 1-day and 30-day mortality were assessed by calendar year. Poisson regression with robust variance estimation was used to estimate both age-and sex-adjusted relative risk of death and prevalence ratios for Charlson Comorbidity Index (CCI) to allow comparison by year, with 2007 as reference year.

Results: The annual number of emergency ambulance service patients increased from 24.3 in 2007 to 40.2 in 2014 per 1000 inhabitants. The proportions of women increased from 43.1% to 46.4% and of patients aged 60+ years from 39.9% to 48.6%, respectively. The proportion of injuries gradually declined, non-specific diagnoses increased, especially the last year. Proportion of patients with high comorbidity (CCI≥3) increased from 6.4% in 2007 to 9.4% in 2014, corresponding to an age- and sex-adjusted prevalence ratio of 1.27 (95% CI 1.16 to 1.39). The 1-day and 30 day mortality decreased from 2.40% to 1.21% and from 5.01% to 4.36%, respectively, from 2007 to 2014, corresponding to age-adjusted and sex-adjusted relative risk of 0.43 (95% CI 0.37 to 0.50) and 0.72 (95% CI 0.66 to 0.79), respectively.

Conclusion: During the 8-year period, the incidence of emergency ambulance service patients, the proportion of women, elderly, and non-specific diagnoses increased. The level of comorbidity increased substantially, whereas the 1-day and 30-day mortality decreased.

Keywords: ambulances; diagnosis; emergency medical services; survival.

Figure 1

Age (in years) distribution among emergency ambulance service patients in the North Denmark Region in 2007 and 2014.

Figure 2

Diagnoses according to International Classification of Diseases, 10th edition, chapters among 148 757 emergency ambulance service patients in the North Denmark Region in 2007–2014.

Figure 3

Distribution of diagnoses according to International Classification of Diseases, 10th edition, chapters distributed by age among 148 757 emergency ambulance service patients in the North Denmark Region in 2007–2014.

Figure 4

Mortality up to 30 days after calling for an emergency ambulance in the North Denmark Region in 2007 and 2014.

Figure 5

Mortality up to 30 days after calling for an emergency ambulance among emergency ambulance service patients with the most frequent hospital diagnoses according to International Classification of Diseases, 10th edition, chapters in the North Denmark Region in 2007 and 2014.