Tuesday, October 19, 2010

The cure with a sting: Eczema cream meant to soothe 'makes skin WORSE'

Yet more ill-researched "wisdom" crumbles. Even theories that are "obviously" true must be tested

For years people with eczema have been advised by doctors to use a cheap emollient cream to soothe their irritated skin. But researchers have now discovered that aqueous cream BP can make the condition worse. Tests show a detergent contained in the cream thins the skin and actually causes irritation.

Although aqueous cream has been prescribed for millions of sufferers from childhood, it is the first time research has been carried out on an ingredient called sodium lauryl sulphate (SLS).

Previously it was thought the ‘stinging’ sensation affecting half of users was due to a preservative or antiseptic in the cream.

In a study by Bath University researchers, aqueous cream reduced the thickness of healthy skin in volunteers by more than 10 per cent in just four weeks and water loss was increased.

Professor Richard Guy, professor of pharmaceutical sciences at Bath, said the remedy was likely to aggravate the dry, itchy rashes that plague eczema sufferers. He said: ‘The skin has a protective barrier layer of lipids, around one eighth the thickness of a sheet of paper, that stops chemicals from getting into the body and keeps moisture in.

‘SLS is a detergent used to mix oils into water-based moisturisation creams to give a nice creamy texture. It’s also used widely in shower gels and other cosmetics. 'Our study has found that rubbing aqueous cream containing SLS into the skin thins this protective barrier, making the skin more susceptible to irritation by chemicals. So to use this cream on eczemous skin, which is already thin and vulnerable to irritation, is likely to make the condition even worse.’

The study was published in the British Journal of Dermatology.


Hard exercise damages your heart

A very thorough article below by Kurt G. Harris MD, a radiologist with a very skeptical approach to accepted dietary wisdom.

He is also derisive about the benefit of statins: "For primary prevention, there is no demonstrated mortality benefit to taking statins".

He also seems to be one of the few health writers who is aware that correlation is not causation. What a guy!

I first saw this study by Brueckmann and Mohlenkamp last spring and I'm a bit surprised that the nutrition and fitness blogosphere hasn't noticed it. I think you may have to be an academically-oriented cardiologist or radiologist to really understand the significance of the findings, as the MRI imaging science is a bit esoteric. Also, it's published in Radiology, which is not exactly Gina Kolata territory.

I'll do my best to convince you of just how disturbing this study should be to those who believe that "aerobic" exercise will make you immortal.....

Mainstream thinking still maintains that lots of aerobic exercise is good for cardiovascular health - to the point where everyone uses the word "cardio" as a synonym for long sessions of aerobic effort. Like the diet-heart and lipid hypotheses, this idea is actually only about 40 years old. In the first half of the 20th century, it would have been thought as absurd as the idea that butter clogs your arteries.

So let's say you want to see just how protective "cardio" is against the number one killer of Americans -coronary heart disease. Instead of just looking for atherosclerosis, though, we want "the thing itself" of actual myocardial damage. Who knows, maybe runners get more plaque but have fewer plaque ruptures or a less thrombogenic blood profile?

So in the Breuckmann study, they recruited 102 active marathon runners. To be a marathon runner (and perhaps to maximize their power to show how healthy "cardio" is) required at least 5 marathons in the past 3 years. Many had run dozens or more in their lifetime. Anyone with a known history of heart disease or diabetes was excluded. The average age was 57 with age 50-72. The median number of marathons was 20. Weekly mileage was 35 (55km). Mean work was 4700 METs per week.

There were 102 totally asymptomatic age-matched controls, also with no history of diabetes, who had no significant history of vigorous exercise.

All subjects had cardiac MRI with LGE imaging. Those with LGE abnormalities were called back to have perfusion imaging as well to help tell if they had evidence for ischemia.

What do you think they found? After all, these were a bunch of completely asymptomatic runners. Conventional wisdom will assure you that only eating copious fiber and making turds like a gorilla could make you healthier than being a serious runner.

Would you believe 12% of asymptomatic marathon runners had evidence of myocardial damage on LGE?

Would you believe that among the sedentary controls only 4% had abnormal LGE?

I am obliged to point out that by the conventional arbitrary criteria used in biomedical publishing, the difference was "not statistically significant". To meet the standard definition, there would have to be a 95% chance the difference is real. Instead, the significance level was 8% by McNemar's test, so there is only a 92% probability that the difference is not due to chance. That's a relief.

Among runners with LGE, there were two patterns of abnormality. In the first pattern, found in 5, there was evidence on perfusion imaging and an anatomic pattern that confirmed these were typical ischemic infarcts. That is, they are evidence of heart attacks due to insufficient blood supply in the distribution of a particular diseased coronary artery. The kind of heart attacks we are all familiar with that kill 500,000 Americans a year. Two of the controls had these classic appearing infarcts.

Runners 5 classic heart attacks
Sedentary 2 classic heart attacks

The second pattern of abnormality, seen in 7 runners and 2 of the sedentary, was non-classic LGE. These areas of dead tissue were found in the middle or outer layers of the heart muscle, rather than the subendocardial layer. They also tended to be more patchy in disrtibution. This non-classical pattern can indicate scarring or fibrosis from non-ischemic injury to the heart muscle, including myocarditis. However, despite lack of evidence for ischemia on perfusion MRI, this pattern can also occur to due coronary microembolization, where a coronary artery is not narrow enough to cause ischemia, yet small bits of plaque break off or tiny blood clots form and plug the arterioles deep in the muscle - causing infarction and permanent scarring in an "atypical" pattern.

The authors speculate that this atypical infarction could be due to exaggerated shear stress related to marathon running and disturbance of prothrombotic and fibrinolytic systems contributing to microthrombotic emboli.

I think that is a reasonable speculation.

Runners 7 non-classic heart attacks
Sedentary 2 non-classic heart attacks

So whether we are looking at classic heart attacks or non-classic, the ratio is about 2.5 or 3 to 1 in favor of being relatively sedentary.

But, you might say, how do we know this LGE is significant? First, there was evidence of ischemia in most of the classic cases even if you don't buy my statement LGE by itself is definitive evidence of a heart attack.

Second, in only 21 months of followup, 1 of 90 runners without LGE had a significant coronary event and 3 of 17 runners with LGE had a significant event. Significant events included two cases of collapse and EKG abnormalities after a race. None died, but all were proved to have severe coronary disease by conventional angiography and were stented or had bypass surgery. This event-free survival was significant by log-rank at the .0001 level.

Third, the median CAC (coronary artery calcium score) in the runners with LGE was 192, and in the runners with no LGE it was 26. This is a big difference and shows that coronary atherosclerosis is tracking the LGE evidence of heart attacks. So it's probably not just thrombogenicity or arrythmias on top of an invariant level of coronary disease.

Now I'll be good and put on my Karl Popper hat for just a second. Maybe the runners all took up running a few years ago and had bad CAD to begin with? Maybe they had not yet run enough marathons to reverse their disease? From another good paper by the same group on the same subjects:

1) The more marathons run, the higher the likelihood of heart disease. The number of marathons run was an independent and significant predictor of the likelihood of myocardial damage.

The runners had about the same prevalence of non-zero coronary calcium compared to age matched controls randomly assigned from a survey population. This was so despite the Framingham risk score being lower for the runners and there being more than 5 times as many smokers among the controls.

2) Compared to age-matched controls, the runners had 40% higher HDL -c (mean of 74 mg/dl) and 18% lower LDL (121) Again, these more favorable lipid risk factors did not show a benefit in calcium scores, which correlate well with atherosclerosis (not heart attack, but coronary heart disease). Statin deficiency, I guess. How many torpedoes before the Bismarck of the Lipid Hypothesis finally sinks?

3) Compared to age and risk factor matched controls (a second set of controls with similar rates of smoking and other risk factors), 36% of runners had a calcium score or CAC above 100, versus 21% of age and risk factor matched controls. (High CAC means more coronary atherosclerosis) So if the "risk factors" like lipids and BMI and such really are helping you, running seems to be doing something to undo the effect.

There are many good references quoted by Brueckmann and Mohlenkamp. Among them is This paper by Kwong and Chan from Circulation. They looked at the presence of LGE as a predictor of major cardiac events (heart attack) and the ultimate relevant end point for us all - death.

They said: "LGE demonstrated the strongest unadjusted associations with MCE and cardiac mortality (hazard ratios of 8.29 and 10.9, respectively; both P 0.0001). LGE remained the strongest predictor selected in the best overall models for MCE and cardiac mortality."

A hazard ratio of 11 for future cardiac mortality is very, very very, high. 1100% more likely to die is gold standard hazard ratio, of the same magnitude as smoking and lung cancer. This makes it hard to doubt the significance of having LGE and would not be seen if there were benign explanations for it.

This makes sense. How could there be a better predictor of whether you will have a heart attack than evidence that you have already had a clinically silent one?

Brueckmann and Mohlenkamp are German, but get points for an English level of understatement: "...It seems safe to state that marathon runners most likely did not have a lower rate of LGE than did the healthy control subjects, who did not regularly exercise."

Do you think that might be why this paper was in Radiology instead of JAMA or NEJM? Is that why there was no press conference before the paper came out? Do you think maybe Kolata or Jane Brody might have told you about this study in the New York Times if the numbers had been reversed? It's time for some Kuhnian iconoclasm. Let's take the hammer to some "normal science".

I think that atherosclerosis is not caused by lack of sustained high-level aerobic ("cardio") exercise. Just like I don't think lack of "cardio" is the cause of the obesity epidemic. I think premature atherosclerois is caused by diet. Our susceptibility to a bad diet is contributed to by genetics.

I think that not only does sustained "cardio" not protect you from atherosclerosis, I think it is quite likely that through repetitive shear stress with endothelial damage and promotion of an inflammatory state, that it promotes atherosclerosis.

Further, I think that "cardio" can precipitate the thromboembolic and acute inflammatory events like plaque rupture - acute heart attacks, even if it does not directly contribute to atherosclerosis, which I think it does.

Could "cardio" promote atherosclerosis and myocardial damage by being confounded by diet? That is, could the wheat, carbohydrate and linoleic acid found in low fat "healthy" diets be more prevalent in marathon runners by virtue of their greater caloric intake of this noxious garbage?

That's a possibility. I think it may apply to cyclists, most of whom seem to eat horribly and who seem to be prone to osteoporosis.

Even if these findings are all confounded by a noxious athletic diet, I still find no grounds at all to believe that "cardio" protects your heart or makes you live longer.

I think a modicum of repetitive physical activity can improve your mood. I like to a run a 5 k every now and then. It feels good and cross-country seems good for your coordination with all the varied terrain. A little cross-country and some sprinting sure seems to make me more functional. I am not under the delusion that it will improve my overall health or my longevity, though.

Same goes for eating vegetables, fiber, antioxidants, and most supplements. No magic foods.

The good kind of exercise, resistance training, makes you more functional and stronger. That is the only sensible definition of fitness if we follow the hippocratic oath with our selves: Primum Non Nocere

I think if you eat the SAD that adding a little exercise may mitigate some damage in a compensatory fashion by improving your glucoregulatory function and sucking up some of that excess glucose. I don't eat the SAD, though.

I vote we keep the terminology. We should keep calling marathons, centuries on the bicycle and hours on those ridiculous stairmasters and treadmills "cardio" to remind us which organ we are likely to be putting at risk.

Running a marathon is looking about as smart as boxing or playing football. So maybe you should stick to crossfit and weightlifting for your exercise. Or TV watching.


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