Posts filed under Just look it up (285)

Stuff has a story  (borrowed from the West Island) headlined “Over 40? Five tests you need right now”.

You might have expected some reference to the other recent news about screening: that the US Preventive Services Taskforce has now joined the Centers for Disease Control in recommending universal screening for HIV (as TVNZ reported).  It’s not clear if New Zealand will follow the trend — HIV infection in people not in high risk groups is less common here than in the US, so the benefit compared to more selective screening is smaller here.   This illustrates the complexities of population screening.  Not only does the test have to be accurate, especially in terms of its false positive rate, but there needs to be something useful you can do about a positive result, and screening everyone has to be better than just screening selected people.

So, let’s  compare the suggestions from Stuff’s story to what national and international expert guidelines say you need.

Two of the tests, for high blood pressure and high cholesterol, are spot on. These are part of the national 2012/13 Health Targets for DHBs, with the goal being 75% of the eligible population having the tests within a five-year period.  The Health Target also includes blood glucose measurement to diagnose diabetes, which the story doesn’t mention.  The US Preventive Services Taskforce also recommends blood pressure and cholesterol tests, though it recommends universal diabetes screening only after age 50 or in people with high blood pressure or people with risk factors for diabetes.

One of the tests recommended in the story is a depression/anxiety questionnaire, for diagnosing suicide risk.  Just a couple of weeks ago, the US Preventive Services Taskforce issued guidelines on universal screening for suicide prevention by GPs, saying that there wasn’t good enough evidence to recommend either for or against. As the coverage from Reuters explains, these questionnaires do probably identify people at higher risk of suicide, but it wasn’t clear how much benefit came from identifying them. So, that’s not an unreasonable test to recommend, but it would have been better to indicate that it was controversial.

One more of the tests isn’t a screening test at all — the story recommends that you make sure you know what a standard drink of alcohol is.

The top recommendation in the story, though, is coronary calcium screening.  The US Preventive Services Taskforce recommends against coronary calcium screening for people at low risk of heart disease and says there isn’t enough evidence to recommending for or against in people at higher risk for other reasons. The  American Heart Association also recommends against routine coronary calcium screening (they say it might be useful as a tiebreaker in people known to be at intermediate risk of heart disease based on other factors).  No-one doubts that calcium in the walls of your coronary arteries is predictive of heart disease, but people with high levels of coronary calcium tend to also be overweight or smokers, or have high blood pressure or high cholesterol or diabetes — and if they don’t have these other risk factors  it’s not clear that anything can be done to help them.

As an afterthought on the coronary calcium screening point, the story has an additional quote from a doctor recommending coronary angiography before starting a serious exercise program.  I’d never heard of coronary angiography as a general screening recommendation — it’s a bit more invasive and higher-risk than most population screening. It turns out that the American College of Cardiology and the American Heart Association are similarly unenthusiastic, with their guidelines on use specifically recommending against angiography for screening of people without symptoms of coronary artery disease.

From the Stephen Wolfram blog, lots of analysis of Facebook friend data with well-designed graphs.  For example, this graph shows how the mean age of your `friends’ is related to your age.

Those under 40 have Facebook friends of about the same age, but after than the age distribution levels off and becomes much more variable.

Tony Cooper has nominated a Bloomberg statistic (being reprinted in NZ) on life expectancy for Stat of the Week.

The `Sunset Index‘ purports to be the average number of years of life after you stop working, with figures ranging from 23.44 for Singapore to 1.49 for Nigeria. New Zealand is somewhere in the middle, with an index of 15.98.  It really isn’t credible that Nigerians who leave the workforce at age 50 die an average of 18 months later, so what have they done wrong?

Bloomberg have calculated life expectancy at birth, and subtracted the retirement age, but if you reach retirement, you’ve already avoided dying for a long time.  The life expectancy at retirement could be quite different from life expectancy at birth.  Since this difference is likely to vary between countries, the `Sunset Index’ won’t even be correct in relative terms.

So, how bad does it get?  If you look at life expectancy data for Nigeria you see that, indeed, life expectancy at birth is about 50 years, but that life expectancy at age 50 is 70.7 years for men and 72.6 for women. The true `Sunset Index’ value would be about 21, and Bloomberg are off by a couple of decades.

The error is less severe in other countries: infant and child mortality has a big impact on life expectancy at birth,  and in Nigeria about one child in seven dies before age 5. Here are a few corrected values for the Sunset Index

• Singapore: 25
• Nigeria: 21
• Iran: 21
• New Zealand: 20
• USA: 16.5
• Bangladesh: 13

The US is near the bottom of the corrected index because it combines a late retirement age (by Bloomberg’s definition — full Social Security eligibility) with only moderately good life expectancy.

Graeme Edgeler says on Twitter

I know many gay couples will want to marry quickly, but there *must* be a couple named Adam & Steve and we should totally let them go first.

Should we expect an Adam and Stephen couple? This is an opportunity to use public data and simple probability to get a rough estimate.

StatsNZ reported just over 5000 cohabiting male couples in 2006. That’s an underestimate of male couples, but probably an overestimate of those planning to marry soon.

I remembered seeing Project Steve, from the National Center for Science Education.  They collect signatures supporting the teaching of evolution from scientists named Stephen (after Stephen J. Gould) — they are currently up to 1268 — and make the point that under 1% of US males are named Stephen.

It turns out that they get this information from the US Census.  The most recent data is 1990 (and, of course, is US) so it’s not ideal, but it will give us a rough idea.  Stephen comes in at 0.54%, and when you add in Stephan, Esteban, Stefano, it still is no more than 0.6%.  Adam is 0.259%.

Under random assignment, then, there would be less than a 1 in 10 chance that there’s a couple called Adam and Steve living together in NZ, and even then they might well not be planning to get married.

[Update: Brendon correctly points out that I missed ‘Steven’, which is actually the most common variant. Apart from demonstrating that I’m an idiot, this doesn’t change the basic message.]

From the New Yorker, a set of graphs showing how median household income varies along each subway line, based on the census tract containing each station.

Here’s the graph if you take the A-train:

(via @brettkeller)

If you want to get Australian census summary data, you can download it from the Australian Bureau of Statistics, or buy a DVD for A$250.

An article in iTNews explains why someone might pay rather than downloading

“You have to click to download each pack individually, and they’ve set the site up deliberately to make it difficult to use a browser plugin to download everything that is contained on the released DVD image,” Bowland told iTNews.

That’s not hyperbole: Grahame Bowland quotes JavaScript code comments that actually say they are trying to make automatic downloading difficult.

Or, the data release is now available using bittorrent, thanks to Bowland, who bought the DVD (this is perfectly legit: the data are Creative Commons licenced).

(via @keith_ng)

I don’t usually bother with general nutrition stories that don’t contain any direct reference to research, but the Herald story about berries was irresistible. There are lots of biologically active compounds in berries, and many of them have been shown to have interesting properties in test-tubes or mice. As you know by now,  this sort of interesting biochemistry is important because it occasionally translates to genuine health benefits, so you should be asking what the human clinical research shows.

If you go to the Cochrane Library (which is free to everyone in New Zealand), and look for clinical research in humans involving blueberries or cranberries you don’t find much. The only topic with enough information to draw any sort of conclusion is on cranberry juice to prevent urinary tract infections. Which it basically doesn’t. The plain-language summary says

JustSpeak is

a non-partisan network of young people speaking to, and speaking up for a new generation of thinkers who want change in our criminal justice system.

I’m linking because they have a good visualisation of the recently-released police crime statistics, comparing the proportion of apprehensions leading to prosecution among Maori and Pakeha youth. The back-to-back bar charts take advantage of the brain’s ability to detect lack of symmetry.

I probably would have left out the homicide category, which has too few to compare, and it would be interesting to see if small gaps between the categories help.

The real problem is in interpretation.  It’s hard to say what you’d expect just from economic differences and differences in where people live, without any differences in how they are treated by police. A higher proportion of prosecutions could mean the police are using their discretion to prosecute more Maori youth, but a lower proportion of prosecutions could just as easily have been interpreted as harassment of innocent Maori youth.

Keith Ng’s annual NZ Budget visualization seems to be up. Go play.

You might also like last years’ one.  And possibly even the 2011 radioactive space donut.

Our only Prime Minister has tweeted an infographic of the new crime figures

In his defense, I will first concede that Mr Key is not regarded as an unbiased source of information, so he doesn’t have the same responsibilities that journalists do.

Still.

One of the basic and classical problems with representing numbers by pictures (apart from the choice of picture) is scaling.  The crime rate was 16% lower in 2012 than in 2008. The blue bottle is 16% smaller in every dimension than the red bottle.  If you just look at the size of the picture, the area of the blue bottle is nearly 30% smaller than the red bottle. If you take the visual metaphor seriously, these bottles have volume, and the volume of the blue bottle would be 40% smaller.

One of the other basic and classical problems discussed in books on misleading statistical graphics is picking two points out of a time series. Using data from Stats New Zealand, we can plot 17 years.

Crime has been decreasing for a long time, at roughly the same rate.  Mr Key’s graph corresponds to the red line.