The trend started before COVID, but it hasn't been normalised for demographics.

The average 60 year old is inevitably sicker than the average 20 year old, and there's an increasing proportion of the former in the UK workforce.

Not to say there isn't a real problem here - the UK isn't doing a great job either on healthcare or, to my mind even more importantly, preventative medicine and public health, but you need to control variables to get a robust conclusion.