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What causes winter excess deaths?
Respiratory viruses are a key player but how many can really be attributed to them? How many can be attributed to influenza? How much a role does temperature play?
Respiratory viruses are a key player but how many can really be attributed to them? How many can be attributed to influenza? How much a role does temperature play?
Even warmer places like California and Australia see a 30% rise in deaths in winter. Equatorial countries, with minimal seasonality to mortality, have year round influenza deaths. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4411750/
However, lower temperatures in the upper airways of the respiratory tract do favour replication of respiratory viruses. https://onlinelibrary.wiley.com/doi/full/10.1002/rmv.2153
Some have attributed deaths to pollution but the seasonal effect is seen as much in rural areas as in cities.
Seasonality in high cholesterol, high blood pressure and low vitamin D levels may all play a part.
Seasonality in high cholesterol, high blood pressure and low vitamin D levels may all play a part.
A quarter of our genes have a seasonality in their expression including genes involved in inflammation which peak in January. It is not clear whether this is a cause or effect of other seasonal variables including viruses. https://www.nature.com/articles/ncomms8000
We have definitely underestimated the contribution of influenza to winter excess deaths.
Community levels of influenza are predictive of deaths from heart disease. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5158013/
Community levels of influenza are predictive of deaths from heart disease. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5158013/
30% of heart attacks are preceded by upper respiratory tract infections. https://www.ahajournals.org/doi/10.1161/01.cir.0000102380.47012.92
Influenza vaccination has been claimed to have caused a reduction in all-cause mortality of between 30% and 50%. https://www.ahajournals.org/doi/10.1161/01.cir.0000102380.47012.92
Across 4 European countries, summer deaths didn't vary but winter deaths varied week to week in a similar way depending on which influenza was circulating. https://jech.bmj.com/content/49/4/373
The European CDC reckon "a substantial proportion of" winter excess deaths can be attributed to influenza with deaths attributed to the underlying medical condition. https://www.ecdc.europa.eu/sites/portal/files/media/en/publications/Publications/101108_SPR_pandemic_experience.pdf
COVID deaths are specific with bilateral pneumonia, sudden unrecognised hypoxias and clotting derangements. This classic clinical picture combined with mass testing has meant that we can be confident that no COVID death will have been left undiagnosed.
Deaths due to in previous years to underdiagnosed influenza will this year be attributed to this year's predominant winter virus -COVID.
