Tracking down the numbers
There was a story on Radio NZ last night, and then in other places
The research is the first in the world to measure the impact of taking numerous medications on fractures in the elderly.
Its findings show elderly people taking several high-risk medications for sleeping, pain or incontinence are twice as likely to fall and break bones as those taking no medication.
As the story says, overmedication in elderly people is known to be a problem — people get put on medications and then not taken off them, and there are interactions, and it’s not good. Some — even many– of the drugs are necessary, of course, but these researchers aren’t the only people who think there should be more regular review of what all medications someone is taking.
This research is trying to quantify the impact on falls and fractures, using a large NZ data set of everyone in NZ who was being evaluated for publicly funded long-term community services or aged residential care. Together with the high-quality NZ prescription data, it’s a good opportunity to look at a large enough group of people to measure fractures.
The media stories all seem to come from the Otago press release. The press release doesn’t include a link to the research paper. It doesn’t even give the journal name. The implication that no-one who reads the story could possibly care about the details is a bit insulting.
I’m assuming the research paper is this one, which is new and has the right topic and authors. The analysis is a bit tricky: a lot of people die without having fractures, and you have to decide how to count them in the denominator over time. They did a sensible analysis, if not exactly the one I would have done.
There’s one problem, though: that paper says, in the Results section of the Abstract:
The estimated subhazard ratio was 1.52 (95% confidence interval: 1.28, 1.81) for those with DBI>3 compared with those with DBI=0 in the adjusted analysis.
That is, the paper’s best estimate is a 50% higher rate of fractures in people taking multiple potentially-risky drugs compared to none. 50% higher is still a problem — they estimate that about 1 in 8 fractures could be prevented if everyone could be taken off these drugs (which, of course, not every one can) — but 50% higher isn’t twice as high, and I couldn’t find the “twice as high” number in the paper.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »
I followed up the story on Radio NZ and its counterpart done as a media release by Otago University.
RNZ reporter got back to me and stood by the ‘twice as likely’ claim as she had spoken directly with lead researcher. The journalist for Otago University said that the article’s stats were checked with the researchers.
It doesnt appear to be a situation of of the numbers being misread by journalists at all.
6 years ago
No, it doesn’t, does it? But either the researcher isn’t referring to the published research or the number is wrong.
6 years ago
What I was most interested in was whether the journalism had just made a error in reporting the research numbers, a typo if you like. Both say they specifically checked the numbers with the researchers. So two different people have checked, so the error wasnt inadvertent from busy people.
6 years ago
Oh yes, definitely. Great idea. Thanks. Sorry if I sounded dismissive.
6 years ago
When algebraic distributive rules are applied to English sentences, the results are ambiguous to say the least. The use of “fall and break bones” begs the question of whether that’s:
– a conjunction – the probability that both things happen to one person; or
– a disjunction – the probability that both things happen but not necessarily to the same person; or
– a conditional – the probability that bones break when a fall occurs; or
– an implication – the probability that a broken bone was the result of a fall.
Do any of those come close to halving when the drugs are excluded? (I imagine that some medications would have neurological effects that would increase the likelihood of falls dramatically.)
And when is a fall, a fall, rather than a trip, stumble, sag, roll, or sprawl?
6 years ago
… ooops … I should rather have said:
– a disjunction – the probability that at one of those things happens “and” (failing that) the probability that the other thing happens.
Also, what about the people who are NEITHER “taking high-risk medications” NOR “taking no medication”? Taking “low risk” medications might be an indicator for (correlated) risks, so excluding them from the comparison seems a bit odd.
6 years ago
They looked at fractures resulting in medical care that the person injured attributed to a fall.
They have previously looked at falls requiring medical treatment, with similar results.
6 years ago