Mar 27 JDN 2459666

This topic is quite personal for me, as someone who has suffered from chronic migraines since adolescence. Some days, weeks, and months are better than others. This past month has been the worst I have felt since 2019, when we moved into an apartment that turned out to be full of mold. This time, there is no clear trigger—which also means no easy escape.

The economic impact of chronic illness is enormous. 90% of US healthcare spending is on people with chronic illnesses, including mental illnesses—and the US has the most expensive healthcare system in the world by almost any measure. Over 55% of adult Medicaid beneficiaries have two or more chronic illnesses.

The total annual cost of all chronic illnesses is hard to estimate, but it’s definitely somewhere in the trillions of dollars per year. The World Economic Forum estimated that number at $47 trillion over the next 20 years, which I actually consider conservative. I think this is counting how much we actually spend and some notion of lost productivity, as well as the (fraught) concept of the value of a statistical life—but I don’t think it’s putting a sensible value on the actual suffering. This will effectively undervalue poor people who are suffering severely but can’t get treated—because they spend little and can’t put a large dollar value on their lives. In the US, where the data is the best, the total cost of chronic illness comes to nearly $4 trillion per year—20% of GDP. If other countries are as bad or worse (and I don’t see why they would be better), then we’re looking at something like $17 trillion in real cost every single year; so over the next 20 years that’s not $47 trillion—it’s over $340 trillion.

Over half of US adults have at least one of the following, and over a quarter have two or more: arthritis, cancer, chronic obstructive pulmonary disease, coronary heart disease, current asthma, diabetes, hepatitis, hypertension, stroke, or kidney disease. (Actually the former very nearly implies the latter, unless chronic conditions somehow prevented one another. Two statistically independent events with 50% probability will jointly occur 25% of the time: Flip two coins.)

Unsurprisingly, age is positively correlated with chronic illness. Income is negatively correlated, both because chronic illnesses reduce job opportunities and because poorer people have more trouble getting good treatment. I am the exception that proves the rule, the upper-middle-class professional with both a PhD and a severe chronic illness.

There seems to be a common perception that chronic illness is largely a “First World problem”, but in fact chronic illnesses are more common—and much less poorly treated—in countries with low and moderate levels of development than they are in the most highly-developed countries. Over 75% of all deaths by non-communicable disease are in low- and middle-income countries. The proportion of deaths that is caused by non-communicable diseases is higher in high-income countries—but that’s because other diseases have been basically eradicated from high-income countries. People in rich countries actually suffer less from chronic illness than people in poor countries (on average).

It’s always a good idea to be careful of the distinction between incidence and prevalence, but with chronic illness this is particularly important, because (almost by definition) chronic illnesses last longer and so can have very high prevalence even with low incidence. Indeed, the odds of someone getting their first migraine (incidence) are low precisely because the odds of being someone who gets migraines (prevalence) is so high.

Quite high in fact: About 10% of men and 20% of women get migraines at least occasionally—though only about 8% of these (so 1% of men and 2% of women) get chronic migraines. Indeed, because ti is both common and can be quite severe, migraine is the second-most disabling condition worldwide as measured by years lived with disability (YLD), after low back pain. Neurologists are particularly likely to get migraines; the paper I linked speculates that they are better at realizing they have migraines, but I think we also need to consider the possibility of self-selection bias where people with migraines may be more likely to become neurologists. (I considered it, and it seems at least as good a reason as becoming a dentist because your name is Denise.)

If you order causes by the number of disability-adjusted life years (DALYs) they cost, chronic conditions rank quite high: while cardiovascular disease and cancer rate by far the highest, diabetes and kidney disease, mental disorders, neurological disorders, and musculoskeletal disorders all rate higher than malaria, HIV, or any other infection except respiratory infections (read: tuberculosis, influenza, and, once these charts are updated for the next few years, COVID). Note also that at the very bottom is “conflict and terrorism”—that’s all organized violence in the world—and natural disasters. Mental disorders alone cost the world 20 times as many DALYs as all conflict and terrorism combined.