Christmas holidays can be a risky time for both your bank balance and your state of mind, but there is also some research indicating it is a time when you are at higher risk of dying from a heart attack.
To date most of the evidence for an increased risk of heart-related deaths over the Christmas period came from a study conducted in the United States over a decade ago. This showed an increase in heart-related deaths outside medical facilities at Christmas time. We wanted to see if this study could be replicated to confirm and extend these findings.
Studies that try to replicate results are important, not only to provide additional evidence on whether the original finding is correct, but also because they allow researchers to examine whether the findings hold true in different populations and conditions.
So, for example, in the northern hemisphere the Christmas holidays coincide with winter. This is known to be a time of high deaths from heart attack due to temperature as well as seasonal variations in levels of vitamin D and cholesterol. Do the Christmas holidays have a similar effect during summer in the southern hemisphere?
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To answer this question we recently conducted an analysis of 25 years of death records from New Zealand. This involved looking at the number of deaths during holiday periods (December 25 to January 7), defined as the red dots in the figure below, compared with the expected number of deaths based on an average that includes the surrounding weeks (the black line).
The figure clearly shows more deaths in winter (edges of the figure) than in summer (middle of the figure)