March 26, 2010 | 7:05 pm

Erroneous Evidence about Enough Exercise

Posted by Albert Fuchs, M.D.

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This week, a study in the Journal of the American Medical Association received a lot of undeserved media attention.  The study wanted to examine the relationship between exercise and long-term weight changes among women who were eating a normal diet (i.e. not dieting).  It followed for over a decade 34,000 women who were 45 years old or older and correlated their self-reported physical activity and body weight.

The study found that on average, the women gained about 6 lb during the study.  Among women who initially had normal weight (body mass index less than 25) there was a significant correlation between amount of exercise and maintenance of weight.  Women with initially normal weight who did at least 60 minutes a day of moderate to intense exercise maintained their weight, while those who did less tended to gain weight during the study.

The authors therefore concluded that for middle-aged women who are not dieting, 60 minutes of moderate exercise daily is necessary to prevent weight gain.  This conclusion was repeated in much of the media coverage (links below) trumpeting that women should be exercising much more than we previously thought necessary.

But hold on a minute!  First of all, the study is observational, not randomized.  If you really wanted to know the effect of different amounts of exercise on weight you would randomly assign women to different quantities of exercise, make sure they were doing the assigned amount, and follow their weight.  That’s not what happened here.  The women exercised as much or as little as they wanted, and that amount was correlated with their weight change.  But that means that anything that affects both exercise and weight could have skewed the results.  Women with chronic illnesses that cause weight gain (hypothyroidism, heart failure) would tend to feel too tired to exercise and also gain weight.  These women would tend to make the statistics look worse for sedentary women, though their weight gain had nothing to do with being sedentary.

Also, the amounts of exercise was self-reported, not observed by someone objective, making it possible that women with stable weights are simply more likely to exaggerate their reported exercise.  (Which reminds me, I have to take it easy this weekend after running 3 marathons and swimming up the Mississippi River this week.)

Finally, the correlation between exercise and weight gain was only found in women with normal weights.  In women who started with a BMI over 25, there was no connection found between how much they said they exercised and how much weight they gained.  Does that mean that overweight people shouldn’t exercise?  No.  It means that there’s nothing to learn from correlations and that we can only learn from a randomized experiment.

So this tells us nothing about how much women should be exercising to maintain their weight.  Perhaps it tells us that some conditions cause weight gain and inability to exercise.  Perhaps it tells us that thin women exaggerate when reporting their exercise habits.  Perhaps it tells us nothing.

So how can you tell how much exercise you need to maintain your weight?  Weigh yourself.  If you’re gaining weight, you should exercise more.

Learn more:

Journal of the American Medical Association article: Physical Activity and Weight Gain Prevention

Los Angeles Times article:  Women should exercise an hour a day to maintain weight, study says

Wall Street Journal article:  New Exercise Goal: 60 Minutes a Day

Important legal mumbo jumbo:
Anything you read on the web should be used to supplement, not replace, your doctor’s advice.  Anything that I write is no exception.  I’m a doctor, but I’m not your doctor despite the fact that you read or comment on my posts.  Leaving a comment on a post is a wonderful way to enter into a discussion with other readers, but I will not respond to comments (just because of time constraints).

March 19, 2010 | 6:29 pm

More Match Day Misery

Posted by Albert Fuchs, M.D.

… or, If We Beg, Will You Go Into Primary Care?

What if tomorrow 30% of the nation’s plumbers disappeared?  Perhaps they vanish due some fantastic science fiction experiment gone horribly wrong.  What would happen?  Would a national plumber group call for making plumbing a more attractive profession?  Would there be a cry for greater federal plumbing subsidies to draw more people from other fields into plumbing?

No.  (Or at least, I hope not.)  In the short term, there would be a terrible shortage of plumbers.  The plumbers available would have more work available then they could possibly complete.  They would have to raise their rates to match demand to supply.  This would have two important benefits.  First, it would force customers to conserve on plumbing services.  As plumbers got more expensive, less important or less urgent jobs would be deferred, since only those with a need that justified the expense would want to pay the higher fees.  Second, plumbers would make much more money than they used to, attracting more people to the field.  People who previously were having a hard time deciding between plumbing and some other field would be more likely to go into plumbing.

Within a very short period of time the number of plumbers would be very close to what it had been before the Horrible Plumber Vanishing of 2010, and their fees would be almost back down to what they were before the HPV.  Things would quickly be more or less back to normal.

Well, a similar but much slower vanishing is happening to primary care doctors.  Yesterday was Match Day, the day on which all graduating US medical students find out the residency to which they have been accepted.  The numbers for primary care continue to look bleak.  The number of medical students that matched to an internal residency was 2,772, up 3% from last year, but 30% lower than in 1985.  Despite this year’s small increase, the overall trend is one of medical students fleeing from primary care into higher-paying specialties.

This is occurring at the same time as our population ages, the baby boomers reach Medicare eligibility, and health care reform promises to add thousands more to the rolls of the newly-insured.  National groups have been warning of a looming primary care shortage for years, and this year’s Match Day numbers only reinforce that concern.

The American College of Physicians (ACP), the national organization of internal medicine doctors (of which I am a member) issued a press release expressing concern about this trend.  Dr. Steven Weinberger, an executive in the ACP, said “it is critical to begin making careers in internal medicine attractive to young physicians”.  Is it?  But why isn’t the problem fixing itself, like the imaginary plumber problem?

The reason is that most doctors can’t increase their fees.  Their fees are set by insurance companies.  The normal market response to a shortage—higher fees followed by more people entering the field—isn’t happening.  So Dr. Weinberger is left urging that Medicaid and Medicare payments should be increased to primary care physicians, a bitter prescription when the costs of these programs are already skyrocketing.

Dr. Weinberger would serve ACP members and our patients more effectively if he realized that pressuring insurers to increase payments to doctors is a tactic that has run its course.  Bankrupting the nation with ever-increasing costs is not a sustainable way to promote primary care.  The surest way to attract more physicians to primary care is to have patients decide for themselves with their own dollars how much primary care they need and how much they are willing to spend for it.  Dr. Weinberger should be encouraging doctors to work directly for their patients.

After all, that’s how we ensure that we have enough accountants and lawyers and plumbers.

Learn more:

American College of Physicians press release:  Residency Match Results Not Encouraging for Adults Needing Primary Care

Los Angeles Times Booster Shots:  Primary care still isn’t an attractive choice for new doctors

Important legal mumbo jumbo:
Anything you read on the web should be used to supplement, not replace, your doctor’s advice.  Anything that I write is no exception.  I’m a doctor, but I’m not your doctor despite the fact that you read or comment on my posts.  Leaving a comment on a post is a wonderful way to enter into a discussion with other readers, but I will not respond to comments (just because of time constraints).

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March 12, 2010 | 12:08 pm

Are Bisphosphonates to Blame for Baffling Bone Breaks?

Posted by Albert Fuchs, M.D.

This week ABC World News aired a story about a possible side effect of osteoporosis medications.  The family of medications involved in this story is called bisphosphonates and includes Fosamax, Actonel and Boniva.  These medications have been proven to prevent fractures in patients with osteoporosis (very low bone density).  Apparently, some doctors had noticed the occurrence of an unusual kind of fracture, a break in the thigh bone between the hip and the knee, in some women who had been taking bisphosphonates for over five years.  Also unusual was that these fractures seemed to be happening with fairly small traumas, without the major impact expected to break a thigh bone.

So, faced with these reports, since television news is known for sober and uncontroversial reporting of well-researched information, ABC decided to hold this story until they checked out whether these fractures have anything to do with these medicines.

Ha!  Just kidding!  Of course ABC ran the story, frightening countless women into believing that they may be at risk for breaking a leg because they are taking a medication specifically to reduce such a risk.  (Actually given the declining broadcast news ratings, perhaps they only frightened the last dozen Americans without cable or internet access.)

Obviously, the important question is:  Are these rare fractures happening more frequently to women on bisphosphonates than to women with osteoporosis who are not taking bisphosphonates?  The most honest answer is:  nobody knows.  Nobody has yet done the counting.

I’m sure we could also find that men taking medication for baldness get sunburns on the tops of their heads more often then other men.  But that might be a consequence of the baldness, not of the medicine.  Similarly, women with osteoporosis are at higher risk of fractures than other women, and every study done so far shows that bisphosphonates reduce that risk.  Whether this unusual thigh fracture is an exception should be the subject of a careful study.  Until then, we just don’t know.

The FDA released a statement (link below) urging women not to stop their osteoporosis medicines without a discussion with their doctors, and reminding doctors that these new reports do not change the indications for using bisphosphonates.

The rest of us got a useful reminder not to get information from TV news.

(Thanks to my patient Joyce for pointing me to the ABC News story and to my friend and colleague Mark for pointing me to the FDA statement.)

Learn more:

FDA Drug Safety Communication: Ongoing safety review of oral bisphosphonates and atypical subtrochanteric femur fractures

Reuters article: FDA rules out bisphosphonate, thigh fracture link

ABC World News story:  Osteoporosis Drugs, Like Fosamax May Increase Risk of Broken Bones in Some Women

Important legal mumbo jumbo:
Anything you read on the web should be used to supplement, not replace, your doctor’s advice.  Anything that I write is no exception.  I’m a doctor, but I’m not your doctor despite the fact that you read or comment on my posts.  Leaving a comment on a post is a wonderful way to enter into a discussion with other readers, but I will not respond to comments (just because of time constraints).

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March 5, 2010 | 6:34 pm

American Cancer Society Revises its Guidelines for Prostate Cancer Screening

Posted by Albert Fuchs, M.D.

About a year ago I reviewed the controversies of prostate cancer screening, especially the conundrum that we still don’t know whether finding prostate cancer early saves any lives.  I concluded by citing the US Preventive Services Task Force (USPSTF) recommendations that the evidence is insufficient to recommend for or against screening for prostate cancer in men age 50 to 75.  The USPSTF recommends against screening men older than 75 as the evidence suggests that harms outweigh benefits in these men.

What does screening for prostate cancer mean?  There are two tests that are used to test for prostate cancer.  One is a blood test called prostate specific antigen (PSA).  The second is the not-always-popular digital rectal exam (DRE) in which a physician physically palpates the prostate in an attempt to feel an abnormality.

In contrast to the USPSTF, the American Cancer Society (ACS) has traditionally recommended more aggressive prostate cancer screening than was strictly supported by the evidence.  This week, the ACS issued revised prostate cancer screening guidelines that better reflect the current uncertainties in the science.  The new guidelines are much closer to the USPSTF recommendations.

The major changes in the new ACS guidelines are:

• A discussion with the patient explaining that the benefits of screening are uncertain and explaining the possible benefits and risks of screening should occur before screening is performed.
• For men who choose to be screened for prostate cancer, DRE is now optional.  Screening can occur with a PSA with or without DRE.
• For men who choose to be screened for prostate cancer and who have a PSA less than 2.5, screening can occur every two years rather than annually.

I understand that for many of my patients avoiding the DRE will be the highlight of their annual exam.  But the bigger point that these guidelines struggle with is the fact that we have no idea whether or not we should be testing men for prostate cancer.  Even worse, we are sure that some of the men who will be tested will be found to have prostate cancer and will be harmed by side effects of the subsequent treatment much more than their prostate cancer would have hurt them.

We will have better studies in the next few years that will attempt to answer if prostate cancer screening saves lives.  In the meantime we have to make difficult decisions in the absence of adequate information.

Learn more:

American Cancer Society Revised Prostate Cancer Screening Guidelines: What Has—and Hasn’t—Changed

Los Angeles Times article:  Education should accompany prostate screening, new guidelines say

Wall Street Journal Health Blog post:  New Prostate Cancer Guidelines: Routine Screening Still Unneeded

My last post about prostate cancer screening:  Screening for Prostate Cancer May Harm More than Help

Important legal mumbo jumbo:
Anything you read on the web should be used to supplement, not replace, your doctor’s advice.  Anything that I write is no exception.  I’m a doctor, but I’m not your doctor despite the fact that you read or comment on my posts.  Leaving a comment on a post is a wonderful way to enter into a discussion with other readers, but I will not respond to comments (just because of time constraints).

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