Death rates among 25–49-year-olds 42% higher in the North than the South of England
(news.liverpool.ac.uk)
They also mention “people under 75”, so I assume they’re just using quarter-century ranges: 0–24; 25–49; 50–74; and 75–99.
Actually, here's a figure from the original study that uses 5-year bands, and you can see the anomaly covers those specific bands (with the under-25 bands looking more like random noise, which I assume is a statistical effect of the low number of total deaths in that range).
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