What's the proper amount of dog for optimal health?

Humans have had dogs as companions for thousands of years. Over that time, dogs have evolved to become ever-better companions, as we humans selectively bred them for traits that we like, such as friendliness and loyalty.

Dog owners already know that owning a dog reduces stress. But it turns out that the health benefits of owning a dog go quite a bit further: two new studies published this month in the journal Circulation both found that owning a dog reduces your risk of dying.

The first study, by Carolyn Kramer and colleagues at the University of Toronto, reviewed ten other studies dating back more than 50 years, covering 3.8 million people. They compared dog owners to non-owners and found that dog owners had a 24% lower risk of dying, from any cause, over a 10-year period. The benefit was even greater for people who'd suffered a heart attack: those who had a dog at home after their heart attack had a 65% lower risk of dying.

The second study, by Tove Fall and colleagues at Uppsala University, focused on the benefits of owning a dog for people who have had a heart attack or a stroke. They used the Swedish National Patient Register to identify 335,000 patients who'd suffered one of these events between 2000 and 2012, about 5% of whom were dog owners. They found even greater benefits than the first study: among people who'd had a heart attack, their risk of dying was 33% lower if they owned a dog as compared to people who lived alone. The benefits were smaller but still significant for people who lived with a companion (a spouse or a child): they still had a 15% lower risk of dying if they also owned a dog. For those who'd had a stroke, the risk of dying for dog owners was 27% lower than for people who lived along, and 12% lower than for people who lived with a companion but didn't have a dog. This study measured the risk over a 4-5 year followup period.

These studies are consistent with many other scientific reports, stretching back decades. They're all consistent, and they all point in the same direction: dog ownership is good for your health. In fact, back in 2013 the American Heart Association issued an official statement on "Pet Ownership and Cardiovascular Risk" with this recommendation:

"Pet ownership, particularly dog ownership, may be reasonable for reduction in cardiovascular disease risk."

However, because the evidence was not very strong, the AHA also advised that people shouldn't get a pet "for the primary purpose of reducing CVD risk." In other words, don't get a dog if you don't want one. As every dog owner knows, owning a dog is much more trouble than simply taking a daily pill.

The new studies strengthen the existing evidence for the health benefits of owning a dog. In an accompanying editorial in Circulation, Dhruv Kazi from Harvard Medical School asks a critical question: is the association between dog ownership and reduced mortality just a correlation, or is it causal? He points out that studies have shown that dog ownership reduces blood pressure and other signs of stress, and that dog owners tend to get outside and walk more (with their dogs). Thus it's very plausible, medically speaking, that dog ownership is good for you. For these and other reasons, Kazi concludes that

"the association between dog ownership and improved survival is real, and is likely at least partially causal."

One final question is still nagging at me, though. Now that we know that dog ownership is good for your health, what's the optimal dose? Would it be even healthier to own two dogs rather than one? And what if we throw in a cat, does that strengthen or reduce the effect? Finally, is it healthier to own a larger dog, or is a small one just as good?

Clearly, more research is needed.

[Note: the author discloses that he owns a rescue dog, a rather small terrier.]

The federal government is wasting over half a billion dollars a year on chiropractic and osteopathic manipulation

A book on the abuses of chiropractic,
written by a former chiropractor

Here's a quick way for the U.S. government to save over half a billion dollars. Stop paying for coverage of medical procedures that have little or no evidence to support them.

The Centers for Medicare and Medicaid Services (CMS) now releases annual reports of how much it spends, broken down according to the procedures. Their latest data, for the year 2015, reveals that Medicare spent $564,165,721 on pseudoscientific medical practices.

I'm talking about chiropractic and osteopathic manipulation. These are similar but distinct belief systems, both involving bones, and both with little high-quality evidence to back them up. Most people think that chiropractors' spinal "adjustments" can relieve pain from injured or aching backs. It turns out that it's just an elaborate placebo: a back rub at home is likely to work just as well. And that home treatment is probably safer–I'll get to that below.

Osteopathic manipulative therapy (OMT) was invented out of whole cloth in the mid-19th century by Andrew Still. Still believed that every part of the body was linked by a mysterious "myofascial continuity" and that manipulating it could treat a vast range of aches, pains, and other ailments. Most of this is not true. (There is some evidence that OMT can be beneficial in carefully selected cases of lower back pain, but the evidence is quite thin (see this review), and the CMS codes don't distinguish different uses of OMT.)

Osteopathic manipulation is what Larry Nassar, the now-convicted sexual predator, claimed he was doing to the hundreds of young girls whom he molested over the years when he was a sports doctor at Michigan State University and a doctor for the U.S. Olympic gymnastics team. (Osteopathic physicians, which is what Nassar was, generally practice real medicine, and I don't mean to suggest that any of them endorse Nassar's awful abuses. However, OMT is a relic of their pseudoscientific past, and Medicare should not be covering it.)

Chiropractic is no better than OMT. It was invented by D.D. Palmer in the 1890s, around the same time that Andrew Still was concocting OMT.  Palmer mistakenly believed that misalignments of the spine, which he called subluxations, caused a vast range of health problems, even infectious diseases. As retired chiropractor Samuel Homola has written,

there is "no evidence at all to support chiropractic subluxation theory," 

but thanks to clever marketing, chiropractors have convinced millions of people to see them on a regular basis. (See chirobase.org for much, much more.)

Even more alarming is that chiropractic adjustments carry a small but frightening risk of causing a stroke, as a result of tearing the vertebral artery, as I've written about before. In fact, the American Heart Association issued a warning in 2014 that "neck manipulation may be associated with stroke". Not surprisingly, the chiropractors association strenuously denied this, but the evidence speaks otherwise. Indeed, a 2015 study that I described when it appeared showed that Medicare patients–the same cohort whom we are paying half a billion dollars a year to provide chiropractic treatments–suffered a significantly higher risk of stroke after seeing a chiropractor than those who instead saw a real doctor.

And a 2003 study in the journal Neurology show an equally alarming increased risk of stroke due to tears in the vertebral artery after chiropractic in younger patients. The lead author of that study, Dr. Wade Smith, warned that

"physicians and patients should be aware of spinal manipulation therapy as a rare but potentially causal factor in stroke."

[Update: note that a 2016 study, in the journal Cureus, found that the link between chiropractic neck manipulation and arterial dissection was not causal; i.e., that chiropractic did not appear to cause arterial tears. However, concerns remain, as demonstrated in this 2017 case report of cerebral hemorrhage following chiropractic activator treatment.]

The 2015 numbers from the Centers for Medicare and Medicaid Services show that the vast majority of the wasted funds, $545 million, went to chiropractic treatments, with another $19 million going to osteopathic manipulation. Neither amount is justified by scientific evidence.

Let's stop wasting our money on procedures that don't help, and may harm, Medicare patients. If we want to help patients, let's insist that Medicare spend our money on real medicine.

An aspirin a day keeps the grim reaper away

Low-dose aspirin is good for you. Any brand of aspirin 

will do, Bayer or otherwise.

Should you take an aspirin every day to prevent some types of cancer? The evidence is growing, and it all points to the same answer: yes.

In 2016, the US Preventive Services Task Force, a science-guided panel that reviews the evidence for a wide range of treatments, recommended regular low-dose aspirin use for people between the ages of 50 and 69 as a way to prevent heart attacks, strokes, and some types of cancer. For people younger than 50 or older than 69, the USPSTF said that the evidence was inconclusive.

The 2016 recommendations came with a caveat: long-term aspirin use carries a slightly increased risk of bleeding in the stomach and intestinal tract, and a small increase in the risk of a hemorrhagic stroke–although it reduces the risk of ischemic strokes. (Ischemic strokes are caused by blood clots in the brain, while hemorrhagic strokes are caused by bleeding. Aspirins reduces the blood's ability to clot, so this tradeoff makes sense physiologically.)

Later in 2016, a study by Yin Cao and colleagues at Harvard found that aspirin use reduced the risk of cancers, especially colon cancer. To be specific, they found a benefit from taking 0.5 to 1.5 aspirin tablets per week for at least 6 years (a standard tablet is 325 mg). For people who followed this regimen, the risk of colon cancer was about 19% lower.

Now, a new study also led by Yin Cao and others at Harvard, just reported in the annual meeting of the American Association for Cancer Research, shows even clearer benefit. They looked at long-term results in a group of 130,000 women (mostly nurses) and men (doctors and other health professionals) who have been followed since the 1980s. Overall, woman had a 7% reduction in the relative risk of dying from any cause and men had a 11% reduction.

Most of the reduction in mortality was due to the reduced risk in dying from colon cancer, breast cancer, and prostate cancer. Just as with the previous study, the benefit appeared in people who took 0.5 to 1.5 aspirin tablets per week for at least six years.

A decrease in the risk of dying by 7-11% seems like a mighty nice benefit from such a simple treatment. For those (like me) whose stomach is upset by aspirin, a low-dose aspirin tablet taken with food may be easier to tolerate. The low-dose pill contains 81mg, one-fourth of a standard tablet, so 2-6 of these per week is equivalent to the 0.5-1.5 tablets that provided a benefit in the latest study.

It's very encouraging when the evidence for a simple, low-cost treatment consistently shows the same benefit. An important caveat is that that if you have any bleeding problems, you should consult your doctor before taking aspirin.

As for me, I've already stocked up on low-dose aspirin. I'm trying the chewable ones first.

NIH distorts report showing risk of stroke after chiropractic

Why would an NIH center try to mislead the public about a newly published study that it funded? Last month NIH’s alternative medicine center, NCCIH, highlighted one of its studies with this headline: “Low risk of stroke after chiropractic spinal manipulation in older patients with neck pain, study finds.” 

This sounds reassuring, unless you read the study. It turns out that the risk of stroke was 10% higher in patients who saw a chiropractor compared to those who saw a regular doctor. Yet NIH wants us to believe that the study found no serious risk.

Why ask this question? Because earlier studies showed a small but frightening risk of stroke in younger people (45 and below) after chiropractic, caused by dissection of the vertebral artery. Strokes caused by a tear in this artery are extremely rare, but even a tiny possibility of a fatal stroke after a chiropractic manipulation is alarming. As Forbes writer Larry Husten reported last August, the American Heart Association and the American Stroke Association issued a statement warning that chiropractic neck adjustments might cause strokes. The AHA stated:

• "Manipulating the neck has been associated with cervical dissection, a type of arterial tear that can lead to stroke.
• Although a direct cause-and-effect link has not been established between neck manipulation and the risk of stroke, healthcare providers should inform patients of the association before they undergo neck manipulation."

I’ve written about this as well, both at Forbes and in The Atlantic Monthly. The risk is small but the consequences can be extremely serious.

So what's in this new study? The study, led by chiropractor James Whedon at Dartmouth College, was a large-scale survey of Medicare claims involving people aged 66 to 99. Its aim was to answer this question: "what is the probability of stroke following chiropractic spinal manipulation, as compared to a control group of subjects evaluated for neck pain by a primary care physician?" Key findings from the study included these (all from Table 2):

                     Hazard ratio for stroke at 30 days

All patients         1.10 (10% increase)

Patients aged 75-79  1.93 (93% increase)

Patients aged 80-84  2.50 (2.5 times more likely)

Patients over 85     3.59 (over 3.5 times more likely)

This looks bad: for all patients, the risk of stroke was 10% higher if they'd seen a chiropractor versus a regular doctor. In the older patients, the risk of stroke after 30 days was 1.9 to 3.6 times higher than for patients aged 66-69. (All four of these results were reported as statistically significant.) Yet the conclusions of the study–and the NIH press release–make no mention of these findings. The study itself concludes only that 

“Among Medicare B beneficiaries aged 66 to 99 years with neck pain, incidence of vertebrobasilar stroke was extremely low. Small differences in risk between patients who saw a chiropractor and those who saw a primary care physician are probably not clinically significant.”

Talk about spin! The study provides no support for the dismissive statement that the increase in risk of stroke after chiropractic is "not clinically significant"; it seems they are trying to downplay their own finding of a statistically significant increase in risk. The NIH’s press release is just as bad: it merely parrots the study's conclusions, opening with the statement that “cervical spine manipulation is unlikely to cause a stroke,” and never mentioning the statistically significant 10% increase in risk or that the study was led by a chiropractor.

Despite the misleading press release, this new study adds to the evidence that chiropractic carries an increased risk of stroke, especially for older patients. As the American Heart Association recommends, patients should be informed of this risk before submitting themselves to a possibly dangerous neck manipulation. And NIH press officers should read the study before issuing a press release.