Battle of the baselines

Which ones are closer to being right?

None of us can know how many people would have died if x, y or z had been different. For the last five years battle lines have been drawn regarding death data. There was the covid model battle, the overall excess death battle and now there are the baby deaths. What we need is other evidence of a mortality problem to settle the battel of the baselines. For infant mortality, there is a clear signal in the sex ratio, the cause of death data (both of which could be due to increased poverty post lockdown) but also in the white to black ratio which does not fit that hypothesis.

The baby deaths battle

Here are USA deaths each year under the age of 1 (2024 and 2025 data is incomplete currently). The trendline for the whole period since 1999 would indicate excess deaths from 2021 onwards despite a low in the year of the virus, 2020. However, if you could argue that 2011-2016 was more representative of recent time and that 2017-2020 were anomalous for various reasons, you could produce a baseline suggesting there were fewer than expected deaths.

There must be a better way to see if babies are dying too much or not!

Figure 1: Total annual mortality rate for under 1 year olds in USA with baselines absed on 1999-2019 trends and 2011-2016 trends.

Thankfully the data can tell us much more.

Sex ratio:
Looking at the monthly mortality rate (based on mid year population estimates) there is a clear excess which begins in April 2021. For the year prior there were fewer deaths than normal. There was a few month reprieve in winter 2021-2022 when respiratory deaths were lower than usual. The excess is present in males and females and by taking a baseline from 2015-2019 we can compare the excess by sex. For all deaths in this age group up to 2019 between 43 and 44.5% were female. However, the overall female ratio has rocketed well beyond what could be dismissed as due to chance and for the excess deaths alone 66% are female. This is highly concerning for a new pathology being present from 2021. The total excess over 2015-2019 expected levels is 1523 for females and 890 for males.

Figures 2a and 2b: Monthly mortality rate (deaths per 100,000) under 1 year olds in USA by sex

Figure 3: Percentage of deaths of USA under 1 year olds that were female with mean trendline for 2011-2019 and a trendline plus 2 standard deviations (<4.55% by chance that a value lies outside this range by random chance) and plus 3 standard deviations (<0.27% by random chance).

Cause of death

There has been a marked increase in deaths of unknown cause in this age group. It amounts to 21% above expected levels for 2021-2023 in males and 23% in females. The proportion of deaths of unknown cause that were coded as Sudden Infant Death Syndrome has fallen from three quaters in 1999 to only half in 2019. I therefore included all deaths of unknown cause. The excess amounts to 634 female and 777 male deaths of unknown cause.

Figure 4: USA mortality for deaths of unknown cause in under 1 year olds with mean trendline for 2011-2019 and a trendline plus 2 standard deviations (<4.55% by chance that a value lies outside this range by random chance) and plus 3 standard deviations (<0.27% by random chance).

Race differences

The racial differences are harder to track because of significant differences to CDC coding and definitions over the whole period. However, for female babies the white:black mortality rate ratio has rocketed above what is statistically significant since 2021 (the dotted orange line). For males there has been a similar but smaller rise reaching statistical significance from 2022. The excess amounts to 1700 white female excess deaths and 1988 white female excess deaths.

Figures 5a and 5b: Female and male mortality rate ratio of white to black babies under 1 years old

In fact, the mortality rate for black or african american infants continued declining in 2021-2023

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Figures 6 a and 6b: Overall annual mortality rate for white babies under 1 year old and black african american babies under 1 year old

Part of the rise includes deaths attributed to covid but it amounts to approximately 350 covid labelled deaths for 2021-2023 which is negligible compared to the total excess.

With three statistically significant and large signals in sex ratio, deaths of unknown cause and race ratio there is indeed a cause for alarm. The rise is real.

In 2021, I reassured friends that when the babies started dying it would all be over. I was so very wrong.