Wednesday, March 9, 2011

High Cholesterol = Longer Life?

The issue of cholesterol is complex, to say the least.  You might not realize it from watching cholesterol-lowering drug commercials, or even from talking to your doctor.  But there is way more to the story than simply keeping your cholesterol low.  This will probably be a frequent topic on my blog, as there are so many aspects of it to be explored, but for today I'd like to focus on total cholesterol.

Check out this very eye-opening paper.  It's an outstanding review of some of the more intriguing cholesterol research, and one of the few papers that I've actually found difficult to put down.  I seriously couldn't stop reading it.  And it blew my mind.

According to several studies, older adults with higher cholesterol live the longest. In fact, groups with the lowest cholesterol levels typically have the highest morbidity rate.  Here's the breakdown from a couple of these studies...  Dr. Harlan Krumholz found in 1994 that old people with low cholesterol were twice as likely to die from coronary heart disease than those with high cholesterol.  Another study of 92 women aged 60 or over found that those with a total cholesterol level of about 270 mg/dl lived the longest.  Those with the highest cholesterol, over 300 mg/dl, were only 1.8 times more likely to die, while the lowest cholesterol group, 154 mg/dl, was 5.4 times more likely to die.

Interesting stuff huh?  That review paper discusses 20 studies just like these, where blood cholesterol levels were either not associated with cardiovascular disease or all-cause death, or there was an inverse relationship.  This quote from the paper sums up the situation quite nicely...

"It is true that high t-C is a risk factor for coronary heart disease, but mainly in young and middle-aged men. If high t-C or LDL-C were the most important cause of cardiovascular disease, it should be a risk factor in both sexes, in all populations, and in all age groups. But in many populations, including women, Canadian and Russian men, Maoris, patients with diabetes, and patients with the nephrotic syndrome; the association between t-C and mortality is absent or inverse; or increasing t-C is associated with low coronary and total mortality. Most strikingly, in most cohort studies of old people, high LDL-C or t-C does not predict coronary heart disease or all-cause mortality; in several of these studies the association between t-C and mortality was inverse, or high t-C was associated with longevity. These associations have mostly been considered as a minor aberration from the LDL-receptor hypothesis, although by far the highest mortality and the greatest part of all cardiovascular disease are seen in old people."

 In case you're having trouble with the terminology, t-C just means total cholesterol, LDL-C means LDL cholesterol.  A couple of key points here...  if cholesterol is the cause of heart disease, then shouldn't it be a risk factor for everybody, regardless of age, sex, or ethnicity?  It should.  But it's not.  While cholesterol levels can be somewhat predictive of one's risk of heart disease, cholesterol doesn't cause the problem.  The second bolded quote is very key as well.  Studies done in older adults, like these ones showing that those with high cholesterol have less risk of cardiovascular disease, should not be taken as an aberration.  By far the highest risk group is adults over 60, so if the conventional wisdom doesn't hold true for them, it doesn't hold true at all.  These studies should indicate that our current thinking about cholesterol is highly flawed.  Cholesterol simply cannot be the cause of heart disease when it is so notoriously unreliable as a predictor of heart disease in the most at-risk populations.  It's that simple.

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