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In my last set of tweets on @MatthewHootonNZ's armchair epidemiological reckons, I emphasised that he does not have the skills to analyse epidemiological data.
In his latest Herald piece, he unfortunately makes rookie mistakes again /1 https://twitter.com/MatthewHootonNZ/status/1296523226974048256
In his latest Herald piece, he unfortunately makes rookie mistakes again /1 https://twitter.com/MatthewHootonNZ/status/1296523226974048256
He includes a table of the 1330 covid cases in NZ; and describes a hospitalisation rate of 4%; with no deaths under 60 years; and "only" a 30% chance of dying in the 80+ group. The gist is he's minimising the risk of covid based on NZ MOH data; but this is really flawed /2
Flawed in two ways: 1. the only variable he is taking into account in his mortality projection appears to be Age; and 2. because he accounts only for mortality and not for morbidity associated with Covid-19. Let's explore these. /3
1. The only risk factor he highlights is Age. Yes, increasing age increases risk of mortality from covid, as we can see even from our small NZ sample. But that's not the only risk factor for dying from covid. /4
This July paper published in Nature analysed other risk factors https://www.nature.com/articles/s41586-020-2521-4. Comorbidities such as diabetes, obesity, asthma, and others are known to correlate with increased risk of mortality from covid. Let's look at these risk factors for the NZ population /5
Diabetes: We have very high numbers of people with diabetes in NZ. An estimated 200,000 people in NZ have diabetes; with the prevalence in Māori & Pacific persons three times higher than NZ Europeans. https://www.health.govt.nz/our-work/diseases-and-conditions/diabetes/about-diabetes /6
Obesity: New Zealand has the 3rd highest obesity rate amongst adults in the OECD, with 1 in 3 adult NZers obese, and 1 in 10 children. Once again, this is disproportionately found amongst deprived communities; Māori and Pacific families /7
Asthma: NZ has one of the highest rates of asthma in the world; the Asthma Foundation estimates 597,000 NZers take medication for asthma (1 in 8 adults, higher for children) with a very high burden of respiratory admissions amongst children amongst deprived families /8
The Nature paper also found that people of "Black" and "South Asian" ethnicity were at increased risk of mortality. It's important to realise that so far our current NZ covid cases are overwhelmingly amongst Europeans. See https://www.stats.govt.nz/experimental/covid-19-data-portal /9
In epidemiological terms, we would refer to our NZ dataset of a miserly 1665 cases (cases! deaths only 22) to be a "biased" sample; with a hopelessly small sample size. In other words, we are unable to draw any accurate predictions on how covid would impact our population /10
from the MOH data we have. We can't look at our MOH data and make inferences that the virus would have this many in hospital, this many dead or chronically affected, etc, as the sample is too small, and not representative of how covid impacts populations as a whole /11
This is why review of the literature, and understanding of other factors is so important. Let's talk about morbidity from covid - what complications can it cause? /12
A paper published in Nature Medicine describes non-pulmonary complications from Covid-19. If it doesn't get you in the lungs, how does it harm you? Amongst those hospitalised or seriously unwell, 30% had acute cardiac muscle injury, up to 30% acute kidney injury, 6% stroke, /13
up to 52% signs of liver injury, 8-9% confusion or impaired consciousness. https://www.nature.com/articles/s41591-020-0968-3. It is clear that this is not seasonal flu. On top of that, there is increasing evidence of a post-covid syndrome, with chronic breathlessness and fatigue. /14
So far, we have understood that we have a very high burden of comorbidities that would make NZers more likely to die or do poorly compared to other countries, and that it would disproportionately affect our Māori, Pasific and South Asian communities. What about other factors? /15
Hooton doesn't discuss this at all - a really, really important variable to consider - our healthcare capacity. In March, prior to lockdown, NZ had a total of 153 ICU beds. https://www.rnz.co.nz/news/national/412529/153-intensive-care-beds-in-country-survey. 153. /16
And, of those 153 beds, just to drive the point home, only 24 were at Auckland City Hospital. Of the 24 ICU beds at our country's largest hospital, only 6 were isolation beds. Those beds are not empty all the time, they run close to capacity. So...we had to lockdown /17
The number of ICU beds was supposed to be tripled. https://www.rnz.co.nz/news/national/415774/icu-beds-increase-as-ministry-tries-to-triple-capacity. I'm not sure if that has happened yet, but even if we had the target 358 beds, that wouldn't even get us close to the figure we would need if things got out of hand. /18
Our healthcare workforce is VERY thin and PPE stocks are in short supply internationally. I work in paediatrics. During Level 4 lockdown, there were plans to completely reorganise health services to treat covid patients. Thank goodness we didn't need to go there. /19
To sum up - Hooton has a LONG way to go to draw any valid conclusions from our MOH data on covid. To form great public health policy, you need more skills than this. You need local understanding of our inequities, health care capacity, and distribution of comorbidities /20
You need to be informed by the literature, and come to considered judgements. This is very sloppy opining, what a shame he didn't contact some of the many very lovely, very experienced epidemiologists and infectious disease experts within his own institution. /end
