Intermediate Report on Hypertension

By Joel Tan🔸 @ 2023-04-03T03:54 (+50)

Note: This report has been superseded by our subsequent Deep Report on Hypertension - please browse that report for our most updated findings.

Summary

Taking into account the expected benefits of eliminating hypertension (i.e. improved health and increased economic output), as well as the tractability of policy advocacy for a sodium tax as well as various World Health Organization (WHO) Best Buy interventions (i.e. mandatory food reformulation; location-based interventions, a public education and mass media campaign, and mandatory front-of-pack labelling), CEARCH finds that the marginal expected value of policy advocacy for these top sodium control solutions to eliminate hypertension to be 49,419 DALYs per USD 100,000, which is around 80x as cost-effective as giving to a GiveWell top charity (CEA).

The full 32-page report may be found on CEARCH's website (report); this post is a high-level summary intended for busy forum readers who are definitely not browsing the forum when they should actually be working.

Key Points

Importance: This is a strongly important cause, with 2.51 * 10¹⁰ DALYs at stake from now to the indefinite future. Around 65% of the burden is health related, while 35% is economic in nature.
Neglectedness: The present global disease burden of hypertension is expected to grow as a result of various factors – especially economic growth (which causes a shift to western pattern diets and sedentary lifestyles), ageing (since older individuals are intrinsically at greater risk of hypertension) and population growth. At the same time, governments are doing little to solve the problem, with only 5% of countries implementing the WHO's Best Buy solutions for hypertension. This is unlikely to change much going forward, as governments have been introducing these effective policies at a rate of 0.8% per annum so far.
Tractability: A solution with moderate tractability is available, in the form of policy advocacy for sodium taxes and the WHO's Best Buy solutions. While the chances of policy advocacy for such sodium control is fairly low, the empirical literature strongly and unequivocally supports the idea that such interventions will help reduce sodium intake and that lower sodium intake will in turn reduce the disease burden of hypertension.

Cluster View

Beyond the headline CEA results, it can be valuable to use cluster thinking (i.e. looking at the issue from multiple perspectives) to inform our decision on whether to channel resources towards a cause area – as CEAs are sensitive to errors, and multiple perspectives offer a way to robustly sense check our quantitative estimate. Employing this cluster view, and looking at the quality of evidence, expert opinion, and multiple critical considerations, CEARCH finds that hypertension as a cause area does indeed look extremely promising.
Quality of Evidence: Overall, the evidence suggests that the intervention is an effective one. For more details, refer to the Tractability section in the report; but here is a brief summary:
- Success rate of sodium control policy advocacy: Using both an outside view (e.g. of past sodium and sugar tax advocacy attempts and of general lobbying attempts) as well as an inside view, our best guess is that policy advocacy for sodium control has a 3% chance of success.
- How sodium control policy affects sodium consumption: Based on the various systematic reviews and meta-analysis, and after robust discounts and checks (e.g. for a conservative theoretical prior of a null hypothesis; for publication bias; and for miscellaneous issues like reporting bias, endogeneity & selection bias), we expect sodium control policy to significantly reduce sodium consumption as follows: (a) sodium tax (-134 mg/day); (b) mandatory food reformulation (-385 mg/day); (c) location-based intervention (-166 mg/day); (d) public education and mass media campaign (-131 mg/day); and (e) mandatory front-of-pack labelling (-135 mg/day).
- How sodium consumption affects health: Similarly, various meta-analysis – even after the same sort of robust discounts and checks employed above – suggest that sodium intake significantly reduces resting systolic blood pressure (n.b. Aburto et al: -3.39 mm Hg); that lower systolic blood pressure reduces cardiovascular risk (n.b. Ettehad et al: every 10 mm Hg fall in BP sees a reduction in risk of major cardiovascular disease events given a relative risk – RR – of 0.8, of coronary heart disease given RR 0.83, of stroke given RR 0.73, and of heart failure to given RR 0.73, leading to a significant 13% reduction in all-cause mortality); and that additional sodium consumption leads to greater risk of CVD (n.b. Strazzullo et al: increase in RR to 1.14 per additional 1880 mg/day of sodium).
Expert Opinion: The experts we consulted agreed that the global disease burden of hypertension is expected to grow in the coming decades, and that preventive solutions – of the sort the WHO recommends and which we assess here – are generally preferable to treatment. For more details, refer to the discussion on the growth of the problem in the Expected Benefit: Improved Health from Eliminating Hypertension section of the report, and to the discussion on potential solutions in the Problem & Solution section.
Multiple Considerations: Beyond the major considerations (i.e. importance, neglectedness and tractability) – as already discussed above, and which hypertension as a cause area scores well on – hypertension also looks promising given various miscellaneous considerations. In particular, we find that potential lines of criticism (e.g. whether sodium control policy leads to substitution with respect to home foods or to sugary food; or whether we pay too heavy a price with respect to diminished freedom of choice and food pleasure; or whether a sodium tax in particular is regressive) are not sustained. For more details, refer to the Miscellaneous Considerations section of the report.

Changelog

The marginal expected value of hypertension as a cause area for effective altruism has dropped from 300x GiveWell at the shallow research stage to 80x GiveWell here (i.e. an almost 4x drop). Here are some of the factors that caused that drop, or that – conversely – led the drop to not be as large as it would otherwise have been.
An important pair of discounts absent at the shallow research stage but introduced here are: (a) for governments' current sodium policy capturing some of the future benefit; and (b) for governments' future sodium policy (i.e. the mere speeding-up effect).
We have updated our modelling of the future disease burden to linearly project forward the trend in DALY burden per capita, and then applying the results to UN figures on global population up to 2100. This is in contrast to our previous approach of a multiple regression of total DALY burden on age-standardized DALY burden per capita, population size, and median age, to find the relevant coefficients, and then projecting forward based on the linear trends in the underlying variables. Our updated model, we believe, is both more conceptually sound and less counterintuitive in terms of the results it produces. Overall, our updated modelling suggests a higher future disease burden than initially expected.
We have downgraded our confidence in the success rates of sodium policy advocacy.
However, given that the intervention being assessed is no longer just a sodium tax but multiple effective sodium control policies – which makes sense, insofar as advocates can push more than one policy at a time, when engaging governments – our tractability figures do get a boost.
Possibly the biggest single driver of the fall in the headline MEV is our far more pessimistic costing, especially since we have re-evaluated the likely amount of time needed for lobbying to succeed (or to evidently fail in such a way as to warrant a shutdown or pivot) as 3 years, rather than just 1.

Caveats

Point estimates are sensitive, and while relying on them is reasonable given that we are ultimately interested in mean estimates, caution is also warranted.
On top of the initial shallow research round where one week of desktop research was conducted, this intermediate research round saw two weeks of desktop research and expert interviews carried out. We have reasonable confidence in our results here, but more research at the deep stage will be needed before we will have high confidence in these findings.
The headline cost-effectiveness will almost certainly fall if this cause area is subjected to deeper research: (a) this is empirically the case, from past experience; and (b) theoretically, we suffer from optimizer's curse (where causes appear better than the mean partly because they are genuinely more cost-effective but also partly because of random error favouring them, and when deeper research fixes the latter, the estimated cost-effectiveness falls). As it happens, CEARCH intends to perform deeper research in this area, given that the headline cost-effectiveness meets our threshold of 10x that of a GiveWell top charity.

Full Report

The full 32-page report may be found on CEARCH's website (report).

Henry Howard @ 2023-04-03T04:40 (+16)

Looking at preventative health as a cost-effective global health measure is great! Haven't read this report in full but some problems stick out to me at a glance:

1. I don't think hypertension is neglected at all. Some of the world's most commonly prescribed drugs are for hypertension (Lisinopril, Amlodipine, Metoprolol are no. 3,4,5 per Google). I also don't think salt reduction is a neglected treatment: Almost every person presenting to a doctor with hypertension will be recommended to reduce their salt intake.

2. It doesn't seem very effective:

sodium intake significantly reduces resting systolic blood pressure (n.b. Aburto et al: -3.39 mm Hg)
...
every 10 mm Hg fall in BP sees a reduction in risk of major cardiovascular disease events given a relative risk – RR – of 0.8

3.39 mmHg doesn't seem like very much, given that a 10mmHg fall is required for a 20% risk reduction if cardiovascular disease risk.

3. People hate being taxed for doing things they like

I don't find your analysis of the reduction of freedom of choice to be very convincing. You dismiss the reduction of freedom of choice because:

food people are eating will be largely the same in terms of macro ingredients, and will taste subjectively the same given reduction within a range as well as gradual implementation

I don't think this is true. Salt is yummy and people know it. Most people with hypertension are already told to reduce their salt intake and many choose not to. They make that choice for a reason, and forcing them or taxing them for doing so would, I think, lead to significant resentment, resistance and distrust of government. People are already suspicious of over-regulation and of the WHO, and I think even a campaign for this sort of thing might cause more trouble than the small chance of success is worth.

Joel Tan (CEARCH) @ 2023-04-04T10:23 (+2)

Hi Henry,

(1) It's true that hypertension is less neglected in the rich world, but: (a) Even in the rich world we incur a cost from hypertension even needing to be treated in the first place (i.e. health burden given that there's always a time gap between identification and effective treatment, plus the economic burden of those drugs and general treatment support). (b) Also the blunt fact of the matter is that developing countries are poor. This has two upshots - one being that they lack the basic infrastructure to deliver drugs effectively (e.g. one expert kept emphasizing how in Africa people in Africa have to walk great distances and wait a long while to get pills); and another is that EA funding would basically have to fund this as a permanent thing (like malaria nets), but that's counterfactually extremely costly.

(2) The falls in BP have significant impact at the population level! Hence the CEA pencilling out to suggest a very cost-effective intervention. It's true of a lot of potential causes/interventions, to be fair - whereby we reduce some small risk by 0.0X% but if you have 10^Y people it can still be cost effective at scale.

(3) Basically citing from the report, "a meta-analysis suggests that food can be significantly reduced in sodium without significantly affecting consumer acceptability, and as the GCAH factsheet says, "gradual (over a few months) but substantial reductions in sodium of processed foods can be made without altering the perceived taste of food", which makes sense given that our taste buds adjust to salt (and sugar) levels and get more or less sensitive accordingly."

That said, I fundamentally agree that it's going to be politically difficult, far more so than other regulatory stuff like mandatory food reformulation - we see something similar for climate change, where people hate carbon taxes but are fine with quotas even though they practically end up costing consumers the same thing. Overall, this goes into the assessment that sodium policy advocacy has perhaps a 3% chance of success - which I think is fairly reasonable/conservative, insofar as it implies that an organization making a concerted effort across 33 countries (for 3 years each), might expect success in just one.

I suspect that an organization that does lobbying in this area might choose to drop the tax stuff if they find it too difficult, and just focus on the regulatory or education aspects.

jimrandomh @ 2023-04-03T08:07 (+1)

People hate being taxed for doing things they like

It's much worse than that; in hotter climates, salt isn't a luxury, it's basic sustenance. Gandhi wasn't being figurative when he said "Next to air and water, salt is perhaps the greatest necessity of life."

Stan Pinsent @ 2023-04-03T20:01 (+3)

I think Ghandi's point nods to the British Empire's policy of heavily taxing salt as a way of extracting wealth from the Indian population. For a time this meant that salt became very expensive for poor people and many probably died early deaths linked to lack of salt.

However, I don't think anyone would suggest taxing salt at that level again! Like any food tax, the health benefits of a salt tax would have to be weighed against the costs of making food more expensive. You certainly wouldn't want it so high that poor people don't get enough of it.

sophie-gulliver @ 2023-04-13T13:31 (+10)

Hi Joel,

Amazing work and well done on trying to wrangle such a complex topic to help inform prioritisation.

I have a few thoughts, especially on the cost side of the equation which may be useful.

On costs, firstly I am not sure that some of your organisational costs are representative.

For example, the costs for Resolve to Save Lives. In 2021 (the year used in your estimation) RSL was split from its parent org Vital Strategies Initiative however this transition was not complete until mid-2022. As such only a very small fraction of activities are covered by this financial report and these activities under the $600,000 grant were for a COVID-19 project (contracted back to Vital Strategies) not for anything to do with salt reduction (this likely was still covered by Vital strategies). There were also no employees on the books. I don't think this $600K figure is a reliable estimate for costs for salt reduction activities. You may wish to look at financial reports for other years and if possible find ones that directly relate to their salt work.

On the Action on Salt initiative, their costs are also very low but I think it is also important to recognise that this initiative is supported by the Queen Mary University London (e.g. their website is hosted by them, many of the volunteer experts are staff). So I don't think this expenditure figure accurately reflects the costs it takes to run this project like volunteer time and other costs borne by others like QMUL.

I think this all means you may be underestimating.

Finally, I think there is also a bigger picture question on costs versus expenditures. Above you are using org expenditures but these are not costs. Expenditures are the dollar outlays by a specific group. For example, the cost of going to university is not just the tuition price paid by students. The cost includes all resources to provide university including public subsidies, charitable support etc. In cost analysis we are interested in all resources no matter who pays.

In your CEA you are assuming a magnitude of positive effects related to the successful reduction in hypertension DALYs from activities of salt taxation, food reformulation, school meals, mass public education and package labelling. While the costs for a small policy advocacy charity to nudge these interventions into being may be small that is not the true cost of these interventions. The costs borne by others to actually put them into practice (e.g. govt, industry, schools etc) would be significant and this is not accounted for even though these costs are instrumental to realising the effects of these interventions that you are claiming.

Because you don't cost in the full cost of these interventions a cross-comparison to a Givewell charity is not necessarily fair. A charity like AMF are responsible for all the costs of running their mosquito net distribution program which support their claimed effects. In your example, you have only costed the relatively small costs of an advocacy charity and left out many other (substantial) costs necessary to realise the effects of these salt reduction activities like paying for mass media campaigns, or changing formulations in factories, or changing food packaging. But you are still claiming all the effects. So it seems to me that the true cost is vastly underestimated and is resulting in a skewed comparison.

Joel Tan (CEARCH) @ 2023-04-14T06:57 (+1)

Hi Sophie,

Thanks for the feedback on RSL/WASSH - that's really useful, and something I'll definitely factor in at the next research stage!

On governmental/implementation costs - I definitely agree that this should be factored in, but just to clarify, the analysis does take this into account, using WHO estimates of the per capita cost of implementing WHO Best Buy policies on sodium (USD 0.03) and on alcohol taxes (USD 0.004, as an imperfect proxy for sodium taxes. Multiplying this with the average country's population size, as well as the expected years in which implementation will occur (as a function of various discounts like policy reversal rates etc), we get the long-term cost of implementation in the average country.

To this, two discounts are applied: (a) a discoutn for the probability that advocacy succeeds (such that the implementation costs are incurred at all); and (b) a discount for government spending in the average country being far less counterfactually valuable than EA funding which would otherwise have gone to top GiveWell charities or the like. In my experience, discount (b) tends to mean that governmental costs aren't as significant a factor as they would theoretically be - but it does depend on the country of implementation (e.g. its fantastically cost effective to get rich world governments to do stuff given the counterfactuals; less so if you're draining sub-Saharan African governments' budgets).

MathiasKB @ 2023-04-03T11:14 (+8)

I went from being very skeptical of sodium's effects on health (sodium is in all the least healthy foods, so it should come as no surprise that people who are unhealthy tend to eat lots of sodium), but after looking over the studies referenced in the report I've changed my mind.

From an individual perspective it makes no sense to care about sodium in-take as long as your blood-pressure is fine, but from a public health perspective a sodium tax seems almost like a free lunch.

Additionally I can imagine that advocating for a sodium tax might be one of the more doable asks one can make of a government and I could definitely see an organization doing sodium tax lobbying succeed.

Joel Tan (CEARCH) @ 2023-04-04T10:27 (+1)

I do think the evidence of sodium->adverse health consequences is very strong, but I'm also more bearish on a sodium tax now compared to the past - it could well be better to focus on the regulatory stuff, which tends to be less unpopular (as we see from climate, where people are fine with quotas but not taxes, even though they are functionally equivalent in their impact on CO2 emissions and prices). Looking forward to talking to nonprofits and advocacy orgs already working on this, and letting you and Jacob know if this is something CEAP might want to pursue!

jimrandomh @ 2023-04-03T08:23 (+5)

I strongly disagree with the claim that sodium reduction does more good than harm; I think interventions to reduce sodium intake directly harm the people affected. This is true everywhere, but especially true in poorer countries with hot climates, where sodium-reduction programs have the greatest potential for harm.

(This is directly contrary to the position of the scientific establishment. I am well aware of this.)

The problem is that sodium is a necessary nutrient, but required intake varies significantly between people and between temperatures, because sweating costs 1g/L. That's why people have a dedicated taste receptor for it, and why they sometimes crave it and at other times find it aversive.

If you sweat a lot and don't consume salt, you will become lethargic; if you drink something with salt in it, you'll immediately bounce back. If you're a manual laborer, and someone sneakily removes some salt from your diet, you'll either compensate by getting more salt elsewhere, or your productive capacity will drop.

If you look at the published studies on sodium through this lens, you will find that they are universally shoddy. Most are observational but measure sodium intake via urine, causing them to be confounded by exercise. Of those that have interventions, basically all of them start by removing people's ability to self-regulate. I don't think I've seen any that check for negative effects not related to hypertension, but I know the negative effects are there because I can remove the salt from my own diet and experience them.

Props for investigating and doing quantitative analysis. If you do proceed from this intermediate report to a deep-dive report or an intervention project, I hope you'll consider the negatives that the academic research thus far has swept under the rug. I think a properly-conducted RCT, one that reduced sodium intake in a vulnerable population and then accurately reported the harms experienced, could have a significant positive impact.

Joel Tan (CEARCH) @ 2023-04-04T10:40 (+5)

That's an interesting perspective! You're right that the scientific experts would disagree strongly on this, and to cite one of them: "While there is some controversy over the idea of a U or J-shaped curve for salt intake and cardiovascular outcomes, the more robust studies show that these use faulty evidence." Another expert adds to this, "In healthy adults, sodium is needed to sustain BP, but we don't observe a J-curve normally: there is sodium in all food, and the kidney is a great engine at holding on to sodium in low sodium settings, such that lower BP is basically almost always better)."

I also don't think it's accurate to say that the evidence is observational. (a) Aburto et al's (2013) meta-analysis of RCTs and prospective cohort studies shows that a reduction in sodium intake significantly reduced resting systolic blood pressure by 3.39 mm Hg; while Ettehad et al's meta-analysis entirely of RCTs shows that every 10 mm Hg reduction in systolic blood pressure significantly reduced the risk of major cardiovascular disease events (relative risk: 0.8), coronary heart disease (relative risk: 0.83), stroke (relative risk: 0.73) and heart failure (relative risk: 0.73), leading to a significant 13% reduction in all-cause mortality). (b) Then there is the Strazzullo et al meta-analysis of both RCTs and population studies, showing that additional sodium consumption of 1880 mg/day leads to greater risk of CVD (relative risk: 1.14).

On the sweating issue (and hence the associated concerns about exercise and whether people in hot climates will be hurt) - I don't think this is an unreasonable fear a prior, but the Lucko et al meta-analysis of RCTs suggests that 93% of dietary sodium is excreted via urine, so basically that should anchor our expectations that this isn't going to be a significant way in which sodium is lost (let alone to such an extent that it has bad health consequences).

jimrandomh @ 2023-04-05T05:58 (+2)

The existence of these meta-analyses is much less convincing than you think. One, because a study of the effect of sodium reduction on blood sugar combined with a study of the effect of antihypertensive medications don't combine to make a valid estimate of the effect of sodium reduction on a mostly-normotensive population.

But second, because the meta-analyses are themselves mixed. A 2016 meta-meta-analysis of supposedly systematic meta-analyses of sodium reduction found 5 in favor, 3 against, and 6 inconclusive, and found evidence of biased selective citation.

Ramiro @ 2023-04-24T10:34 (+2)

[...] this post is a high-level summary intended for busy forum readers who are definitely not browsing the forum when they should actually be working.

You have just become my favorite EA-charity.