Friday, December 21, 2007

Better Living Through Chemistry II

Brad DeLonglinked to an old post of mine. Over at his blog, there is a debate over statins.

The fact that pharmaceuticals have side effects does not imply that such side effects are bad. For example, the most white bread garden variety pharmaceutical is aspirin. Decades after massive use began, it was discovered (and I mean proven in a genuine double blind experiment with 20,000 subjects) that ... causes reduced risk of heart attack.

On topic, there is epidemiological evidence that statin use is correlated with a reduced risk of dementia

. It is possible that the causation is that the demented are less likely to use statins, 5 minutes of googling did not yield a significant benefit found in a prospective study and one with a point estimate very close to zero effect.


brad said...

Now what is the *mechanism* by which aspirin reduces heart attacks? And what is the mechanism by which statins reduce cholesterol? And what is "insulin resistance" anyway?

Brad, lazy

Robert said...

answers from Dr Robert Waldmann PhD (not licenced to practice medicine). Caveat Lector. I am not an MD. Don't get medical advice from an economist.

Aspirin works by blocking the synthesis of (all) prostaglandins -- a complex set of hormones

which are released by damaged cells. One prostaglandin (prostaglandin e1 I think) is

is responsible for many aspects of the bodies response to injury including tenderness (a touch becomes painful) inflamation and increased blood clotting. Heart attacks are caused by blood clots

(which form because of arterioschlerotic plaques but it's the clot that finally kills).

However, the prostaglandin system is very complicated and includes other hormones (prostacyclin I think) which reduces blood clotting. There is strong evidence that the aspirin effect is not monotonic.

A study with a small dose and a sample of 20,000 showed a protective effect. An earlier study with a larger dose and a sample of 5,000 showed no effect.

Statins inhibit an enzyme involved in cholesterol synthesis.

Insulin resistence refers to the kind of diabetes caused by obesity (called adult onset but kids are getting it in the USA). Classical diabetes (called juvenile onset) is caused by the immune system killing the insulin producing cells in the pancrease. It used to kill quickly, but can be managed with insulin.

Diabetes means high levels of glucose in the blood (actually it means urinates a lot and melitus means sweet). Insulin is a hormone which stimulates cells to remove more glucose from the blood. With obesity age etc., many people have high blood glucose even though their pancrease makes insulin normally. Thus the glucose level resists insulin so it is called insulin resistence.