Life with Hazard Ratios

This is missing the most important thing which is why HRs are so damn useful. It's because (a) survival analysis is very statistically powerful, but (b) many survival curves do not follow a very well-described parametric function. The genius of David Cox was in realizing that, when proportional hazards hold, you can just cancel out the unknown survival function and get the multiplicative hazard ratio immediately, in a statistically powerful and statistically efficient manner. Extremely useful if you are, say, trialing a novel chemotherapy drug and want to end your trial ASAP to get everyone on the intervention arm if the drug actually works.

The places where proportional hazards gets squirrely (very long observation times, crossing curves) are a small fraction of the use cases of survival analysis, and dunking on them for "not being Bayesian" or whatever misses this broader context.

From the article:

> This is essentially the observation Keyfitz made in his 1977 paper, “What Difference Would It Make if Cancer Were Eradicated?” Cancer is responsible for 18 percent of deaths, so does that mean eradicating it would increase lifespan by 18 percent, or around 13.6 years? Nope, Keyfitz says, it’s only 2.3 years.

A very interesting thought!

The most important part of this for a living human being is touched on at the end. You only die once. Life expectancy is an ensemble mean over a population, and "you are not a population". You need to try to avoid risks that are going to kill you personally, not risks that affect aggregate life expectancy (there's overlap of course). Tinkering with HR-translated-to-life-years I think actually blurs that focus for individuals.

The worst case is a risk that has a low ensemble HR and low life years impact, but will kill you personally very soon if you take the wrong action. Eating peanuts has an HR of 1, unless you are prone to fatal anaphylaxis from peanuts. HRs are useful for (and biased towards) doctors protecting as many humans as possible, but as an individual you should try to discover your peanut allergies as early as possible and protect yourself against them.

> 54,786 chambers

365 days * 75 years = 54,750 chambers. 365.25 days (for leap years) gets to 54,788.

Where did the two days go?

I read it, and it seems like the core formula is ΔL ≈ ln(1 / HR) × 12.93 years (for U.S. males). It also gives you an easy way to approximate and interpret HR values from health studies, like an HR of 0.90 roughly translates to a little over a year of added life expectancy. Makes it easier to read those papers.

Personally, I found it interesting. But what I'm curious about is this: are there any studies where the lower your exposure to risk, the shorter your lifespan gets?

I've been thinking about this because I recently saw a story about an ultra wealthy guy who tried a reverse aging experiment and ended up with an incurable disease. This person probably had the best diet in the world and received top tier care, so how did he end up with something like that? It makes me wonder, maybe the human body just rejects reverse aging itself. Maybe we're wired to die because that's how species diversify. Just curious.

Statistics and other lies.

One interesting point the article touches - there was a study concluding that if you quit smoking at 40 your life expectancy basically equalizes with people who did not smoke in their life. It is an encouraging message that it is never too late to quit. Then again it also sends a different message - you can smoke as you wish in your 20s.

Just yesterday I saw an article on Instagram that they are putting smoked meats and sausages and similar products in the came cancerogenic category as smoking. Which again one one hand states that meats are very bad for you. On the other hand it makes smoking not so bad as you would think? Because people are eating sausages and meats cooked on open fire for thousands of years?

Some guy on Diary of CEO states that rice are basically a poison because they are pure sugar. If you want to live healthy you should definitely drop the rice out of your die. Then again a billion of people eat rice every day. What gives?

We want to have all this information because we want informed decisions in our lives. If we are analytical we even want formulas and graphs just like in this article. What we don't want is to give things to chance and genetics.

Different breeds of dogs have life expectancy difference of ~50%. People of course are not so different in their size but we need to always keep this in mind. You can live as healthy as you like but you always have a ticking bomb in your DNA. What I still am not getting is how much living healthy impacts the outcome versus the genetics. It might be a hopeless fight to e.g. stop eating the brisket if your lungs have an expiry date of 55 years.