I put it in inverted commas because natural causes is not a scientific term or a “real” cause of death (though note the difference between scientific and legal cause because in the UK “natural causes” or “old age” can be official causes on a death certificate, watch I think is ridiculous in 2022). “Natural causes” is a blanket term for thousands of possible causes. As Toast said, many families prefer to use it in order to keep specific medical details private.
“Natural causes” covers anything from 200+ cancers, undiagnosed heart conditions (either genetic eg congenital heart defect, or developed eg heart disease), strokes, haemorrhages and aneurysms, SADS, as well as any form of neurological, viral, bacterial condition etc.
And if you think a 53 year old cannot die of natural causes, know that one of my current clients is a 35 year old man on his 2nd heart attack, 2nd stroke, and has narrowly survived double pneumonia, COVID and septicaemia. His body is fucked because he never looked after himself. Lived off of takeaways and never brushed his teeth for a start (which is strongly linked to heart disease). Long story short is you can die of natural causes at any age, but in many cases you can delay it for a very long time by taking care of yourself. Some are unavoidable though – the Nolans clearly have a genetic history of cancer. Laura Branigan and her family had a genetic history of aneurysms. The consequences of genetic conditions can be delayed or reduced by due diligence but they’re harder to swerve completely… it’s best not to think about them too often. Not much you can do.