Vlak MH, Algra A, Brandenburg R, Rinkel GJ. Prevalence of unruptured intracranial aneurysms, with emphasis on sex, age, comorbidity, country, and time period: a systematic review and meta-analysis. Lancet Neurology 2011 Jul.;10(7):626–636. PMID 2164128
With all the talk of how we investigate ? SAH this has some relevance. I was always taught a number of 2% as the number of unruptured aneurysms in the general population.
These guys did one of the big reviews on this in 1998 and are now sensibly updating it with all the more recent studies done with the new imaging techniques.
Apologies if I’m just sharing my own ignorance with my ignorance of epidemiological terms
METHODS
- systematic review type thing – this isn’t my strong point. I tend to just trust them that they’ve looked… naughty i know
- they calculate prevalence ratios which I also don’t really understand but they seem to be a factor of the disease being present and exposure. I may have got that all tits up but check out this and correct me if I’m wrong
- they also calculate crude percentage as a number I can understand
- 68 studies that met inclusion criteria that meant 94912 pts and 1450 unruptured aneurysms
- at a very crude level that seems to me a prevalence of 1.5% (though I suspect that’s skewed by lots of very young people…)
- they report a prevalence of 3.2% in a population without comorbidity with a mean age of 50 and 50% male. In their last study it was 2.3%
- they found all the usual associations (measured by probability ratios) of autosomal dominant kidney disease, and first degree family history
- note they didn’t find an association for smoking, high BP or heavy alcohol but that’s because these populations weren’t specifically in the studies analysed
A FEW THOUGHTS
When I was told that kidney disease and family history were risk factors for SAH I’m not entirely sure if that was based on actual data that people with those RFs were more likely to have SAH or if it was extrapolated from the idea that people who are more likely to have aneurysms are more likely to rupture.
This is illustrated a little bit in this study as they tell us that people in finland are more likely to have SAH but they found no increased incidence of unruptured aneurysms in Finland or Japan.
BOTTOM LINE
Lots of people have aneurysms. They’re mainly small. They’re usually irrelevant. It’s still a bugger to work out what to do with them.
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