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Seasonal variations in out of hospital cardiopulmonary arrest
J P Pell1, J Sirel, A K Marsden
1Department of Public Health Medicine, Greater Glasgow Health Board, Dalian House, 350 St Vincents Street, Glasgow G3 8YU, UK. jill.pell@glasgow-hb.scot.nhs.uk
Insights
Survival rates for out-of-hospital cardiopulmonary arrest are lower in winter. Even after accounting for risk factors, winter arrests show a poorer prognosis, highlighting seasonal disparities in cardiac arrest survival.
Area of Science:
- Cardiology
- Public Health
- Emergency Medicine
Background:
- Seasonal variations in health outcomes are increasingly recognized.
- Out-of-hospital cardiopulmonary arrest (OHCA) survival rates vary significantly.
- Understanding factors influencing OHCA survival is crucial for improving emergency medical services.
Purpose of the Study:
- To investigate potential seasonal differences in survival rates following out-of-hospital cardiopulmonary arrest.
- To identify if winter months are associated with poorer OHCA survival outcomes.
- To analyze the impact of season on OHCA patient characteristics and survival.
Main Methods:
- A prospective cohort study was conducted using the Heartstart (Scotland) database.
- 10,890 patients experiencing OHCA during summer or winter between 1988 and 1997 were analyzed.
- Univariate and multivariate analyses were performed to compare survival rates between seasons, adjusting for patient demographics and clinical factors.
Main Results:
- Survival to hospital discharge was lower in winter (6%) compared to summer (8%), with an odds ratio of 0.77 (p < 0.001).
- Patients experiencing OHCA in winter were older, more likely to arrest at home, less likely to have a witness, and less likely to receive defibrillation.
- After adjusting for case mix, winter OHCA patients remained 19% less likely to survive compared to summer patients.
Conclusions:
- Individuals suffering cardiopulmonary arrest during winter have a significantly reduced likelihood of survival.
- While increased risk factors contribute, poorer prognosis in winter persists even after statistical adjustment.
- These findings underscore the need to address seasonal disparities in OHCA outcomes.
Objective:
To determine whether there are seasonal variations in survival following out of hospital cardiopulmonary arrest.
Design:
Prospective cohort study using the Heartstart (Scotland) database.
Setting:
All of Scotland.
Patients:
10 890 people who suffered out of hospital cardiopulmonary arrest in the summer or winter between December 1988 and August 1997 inclusive.
Intervention:
Univariate comparisons of 5406 arrests occurring in summer with 5484 in winter, in terms of patient characteristics, management, and survival using chi(2) and Mann-Whitney U tests. Multivariate analysis of the association between season and survival following adjustment for case mix.
Main Outcomes Measures:
Survival to discharge from hospital, survival pre-admission, in-hospital survival.
Results:
Only 6% of people who arrested in winter survived to discharge, compared to 8% of those who arrested in summer (odds ratio 0.77, p < 0.001). People who arrested in winter had a poorer risk profile in that they were older, more likely to arrest at home, less likely to have a witness, and less likely to receive defibrillation. However, after adjustment for case mix, people who arrested in winter were still 19% less likely to survive compared to those who arrested in summer. Deaths pre-admission were significantly higher in winter (odds ratio 1.18, p < 0.05) but in-hospital deaths were not.
Conclusions:
People who suffer cardiopulmonary arrest in winter have a significantly lower likelihood of surviving. This is, in part, caused by the higher frequency of a number of recognised risk factors. However, their prognosis remains poorer even after adjustment for these factors.