Recent Non-Covid Excess Mortality. Too much of a bad thing?

This work suggests estimates of non-Covid excess mortality calculated using historic averages lead to 50 to 100% higher estimates than methods incorporating trends.

Excess mortality is a concept that represents the difference between observed mortality and the mortality we would expect to see under ‘normal’ conditions. 

For example, the current excess deaths in week 37 reported by the ONS in England and Wales are 10.4% above the average.

As we have shown, there have been reports of significant non-Covid excess mortality across the world: the number of deaths left after subtracting deaths associated with Covid compared with a reference period. As the mortality we expect cannot be observed directly, it needs to be estimated, and this creates a problem – how should it be calculated? 

This is often done using historical averages – commonly, the average of the previous five-year death totals for any given week. Often called the reference period. 

Using historic averages to estimate the expected mortality works well if the trend in deaths is stable. However,  if the trend increases over time, the historical average would tend to underestimate the expected …