Posts written by Thomas Lumley (2585)

As everyone has reported,  the number of sheep in New Zealand continues to go down, due to land being used for forestry and cattle farming.  The number of people continues to go up, because… you probably don’t need me to tell you where people come from.

As a result, the average number of sheep per person continues to fall

On the other hand, the median number of sheep per person has been at zero for quite a long time.  Some people have lots of sheep, but they are outliers.

After the US started being more unfriendly to visitors, there were analyses showing a sharp fall in visitor numbers “year on year”.  The NY Times has a story about changes in international travel showing it’s a bit more complicated than that:

During the second half of March and early April the year-on-year comparison showed a drop because last year’s data included the Easter peak and this year’s didn’t.  Some people jumped to conclusions about the drop, attributing it to visitors being worried about border control.  We can now see that it wasn’t.

The Times goes on to look at bookings for summer travel to the US, where there do seem to be real decreases.

There’s a Herald story about lotto wins.  It has a sub-headline ‘Luckiest’ Lotto stores in New Zealand

The story admits that Lotto has stopped pretending ‘lucky’ stores exist:

Certain Lotto stores have long been tipped as being “luckier” than others, although Lotto previously stopped promoting this in its press releases after it was criticised by academics for misleading customers.

As you’ll know, other academics (ahem)  also criticised them for misleading consumers.

The Herald then goes on to give us a list of ‘luckiest’ stores.

Q: Did you see  Every bite of ultraprocessed food will increase your chance of an early death.

A: How could they possibly have shown this?

Q: New study says

A: But think about it. How do they measure people’s consumption of ultraprocessed food down to the single bite level? How do they find a comparison group with just one bite less consumption? What does it even mean?

Q: Don’t I get to ask those questions?

A: <sigh>

Q: Where is the new research? And how many people or mice did they study?

A: It’s in the American Journal of Preventive Medicine, and it doesn’t involve any new data collection.  It’s a combination of a bunch of existing studies that looked at correlations between diet and health

Q: Does the claim about “every bite” appear in the journal paper?

A: No.

Q: Where does it come from?

A: As text, I’m not sure.  As an idea I think it comes from a claim in the paper for a “linear dose-response relationship”, ie, that risk goes up in a straight line with consumption of ultra-processed foods

Q: Does it?

A: That’s the model they assumed. They don’t really seem to have assessed the evidence for non-linearity in the paper, and they certainly can’t say anything meaningful about the “single bite” dose. The combined estimate is that groups of people whose consumption of these foods was higher by about 10% of their diet had a risk of premature death that was about 3% higher.

Q: But what would the risk from “one bite” be?

A:  You mean if the relationship was exactly linear extrapolated way down to that level and perfectly causal?

Q: Yes, just for fun

A: One bite of what? Different bites have different calorie levels

Q: Just work with me here. Make something up, ok?

A: Ok. So if one bite was 2% of one day’s energy intake it would be  0.0055% of one year’s energy intake, or 0.00055% of ten years’. At a increase of 3% per 10 percentage points, that’s an increased risk of premature death by a factor of 1.000016.  Which would be quite hard to detect.

Q: We were promised comparisons

A: Ah, yes. The BBC also wrote about this study, with the perfectly reasonable headline Ultra-processed foods may be linked to early death

Q: “May be“?

A: As one expert they quoted said “It’s still far from clear whether consumption of just any UPF at all is bad for health, or what aspect of UPFs might be involved. This all means that it’s impossible for any one study to be sure whether differences in mortality between people who consume different UPF amounts are actually caused by differences in their UPF consumption. You still can’t be sure from any study of this kind exactly what’s causing what.”

Q: He’s not saying ultra-processed food is good, though?

A: No, I think the most negative opinion you’ll see is just that it’s not necessarily a helpful way to categorise food

Stuff has a piece by Lloyd Burr on whether more New Zealanders have been having problems at the US border.  There’s a denominator problem: we want to know not just how many people are detained, but how many travellers that’s out of.

Both numbers are a bit unsatisfactory, and it’s mostly the fault of the Ministry of Foreign Affairs and Trade. We read

Last week, the Ministry of Foreign Affairs and Trade (MFAT) said eight New Zealanders had been detained at the US borders since Donald Trump came to power in November 2024, with another person arrested for “immigration-related reasons”.

A government department that pays close attention to foreign affairs might notice that Donald Trump did not in fact “come to power” in November 2024. The election was in November, but the US has an unusual policy of delaying the actual transfer of power to late January, the week before Auckland Anniversary Day.  The allegations of aggressive border enforcement didn’t start immediately after inauguration, but you might still reasonably start the clock on January 20th.

MFAT said the rate was similar to pre-Covid, which is somewhat helpful. Stuff asked (good to see!) about the comparison to last year, and got the reply that the 2023/24 financial year had nine incidents, the same that we have now seen in the shorter time since November or perhaps January.  The right comparison would depend on how many NZ citizens (since they’re the people who will get consular assistance  from MFAT) had actually travelled to the US in that time period. I don’t know that number, but MFAT should know it or at least be able to get a good estimate if they were feeling helpful.

The NZ$ Herald (from the Telegraph) has a headline Five surprising everyday medications that can help prevent dementia. This is surprising, because the general consensus is that we don’t really have any medications to prevent dementia.

The first example is the shingles vaccine. Here there’s actually some evidence — a ‘natural experiment‘ in Wales, where the roll-out of the vaccine meant people born just before and just after a particular date had different eligibility.  This isn’t quite a randomised trial, since there are other things that vary by birth date, but it’s better than the usual correlations. In particular, it’s better because the claimed effect is pretty small: a 20% reduction in risk, which is much too small to see reliably in the usual correlational studies.  This one is also good because any dementia prevention is a pure bonus; you should already want to get the shingles vaccine to prevent shingles.

Next in the story are statins, the widely-used cholesterol-lowering drugs.  Here the headline evidence is correlation, saying a reduction of 13% in dementia risk was seen in statin users in a Korean study. People have been suggesting statins as dementia prevention for at least twenty-five years and the main change is that the estimates of benefit have gotten a lot smaller.  Again, it may not matter a lot whether this is true — if you’d benefit from statins for dementia prevention you’d probably benefit from them for heart attack prevention.

Viagra is always popular in settings like this — it’s already a repurposed drug, and it’s relatively safe — but for Viagra we don’t even have correlations, just the claim that it opens up smaller blood vessels and that maybe nitric oxide (which Viagra increases) is related to memory in some way we haven’t discovered.

The trendy new drug semaglutide is on the list, again for correlations.  It could be that they really prevent dementia (and if so, we will find out from clinical trials now underway) but it’s also quite feasible that it’s just correlation.  The basis of the claim is that people who got a new expensive injected treatment in short supply for diabetes had fewer new cases of dementia in the short term than people who got a standard drug treatment. This could easily be reversing cause and effect — people with mild pre-dementia symptoms could easily be less likely to get the fancy new drugs.  In New Zealand, it doesn’t really matter if Ozempic prevents dementia, since you can’t actually get it.

And finally, the old TB vaccination that we don’t use any more is on the list. That’s actually somewhat supported by randomised trials, but the trials are in bladder cancer patients who get the BCG bacteria injected into the bladder rather than being trials of ordinary vaccination.  More research is needed before this one could really be described as “can help prevent dementia”. It’s also worth noting that we stopped routine BCG vaccination for a reason: being vaccinated means you can’t straightforwardly be tested for TB exposure.

Overall, this is another example of the “aliens” problem with dementia research.  There aren’t any breakthroughs and there are very few promising treatments. It’s a very hard problem, like detecting alien life, so the news we get is either  genuine early research — “planet hundreds of light years away is the right temperature for liquid water” — or it’s crop circles and flying saucers.

• Jessica Mackenzie on the “dire” wolf story, and how it got that way: “It’s important to consider how sausage like this is made, and I mean the stories—not the actual wolves.”
• Visualisation of the “demise of the love song” from pudding.cool
• Proportions and totals: is the individual risk of Alzheimer’s going down over time? (apparently, yes, even though the total number of cases goes up with the number of older people)
• Australian Associated Press fact check: Claim – 710,000 new voters on the electoral roll include migrants who arrived under Labor.  False: Migrants who arrived under Labor are not eligible to vote in the 2025 election.
• Stuff headline: Traffic ‘worse than Auckland’: Is this New Zealand’s most ‘anti-car’ city? We’re seeing proper use of headline single quotes here — ‘worse than Auckland’ is an attributed quotation in the text. It is, however, attributed to a single motorist.  Headlines about traffic density/slowness really shouldn’t just be one person’s opinion — traffic is measurable, and measured.

The International Statistical Institute is a professional organisation of statisticians. Its membership includes quite a lot of expertise on the production and use of official statistics, and it has a habit of commenting on political interference with official statistics.

The ISI has a statement on US official statistics

The International Statistical Institute (ISI) is concerned about government interference in the compilation and availability of Federal Statistics in the United States of America (USA). A proposed change in measuring and reporting U.S. Gross Domestic Product (GDP) serves as an important and timely example.

The statement goes on to explain that the USA has proposed removing government expenditures from GDP, and that this is both intrinsically a bad idea and also a weakening of international agreements on which official statistics to measure and how to define them.

[Disclaimer: I’m a member of the ISI, but I wasn’t involved in any way in producing this statement]

• Coffee nerd James Hoffman has a good video on an issue that crops up a lot on StatsChat — totals vs means/rates — though in his case it’s about shorter vs longer espresso shots for making flat white/cappucino.
• From Axios: foreigners don’t seem to be visiting the US as much — this is more interesting than it sounds, since a lot of the dip must be short-notice cancellations, which are relatively difficult/expensive.
  
• According to the NZ Herald, Elon Musk wants zero tariffs between the US and Europe. The story doesn’t point out that was very close to the situation a week ago (eg, according to economist Justin Wolfers.)
• Friday’s rain pushed the Auckland dam water levels up nearly four percentage points (conveniently, the total storage is close to 100 GL, so 1 GL is about 1 percentage point), which was bit more than a third of the deficit from average.  While we’re being nitpicky, that should be 9.99% below, not “-9.99% below”
  
• New York has a new subway map
  

Tim Welch has produced a nice Auckland Cycleways Dashboard (it’s a draft at the moment, or ‘beta’ as we nerds say).

Here are some of the University-relevant routes (click to embiggen, as usual)

These are based on the Auckland Transport cycle counters, which are good for the city centre and major bike paths, but less informative for, say, people commuting in from the south, where there aren’t bike lanes or bike counters.