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Harvard Commentaries
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School

What Your Doctor Is Reading What Your Doctor Is Reading

Update From the Medical Journals: June 2014

June 30, 2014

By Mary Pickett M.D.

Harvard Medical School

What's the latest news in the medical journals this month? Find out what your doctor is reading.

Sleep Apnea Treatments Improve Heart Health and Metabolism

Two studies published in the New England Journal of Medicine June 12 looked at two treatments for sleep apnea — weight loss and the CPAP (continuous positive airway pressure) mask. The results show that both should help reduce the risk of heart and blood vessel disease for people with sleep apnea. The first study enrolled 318 people with sleep apnea. This study's main finding was that blood pressure was significantly lower in the CPAP group compared with patients who received oxygen without a CPAP mask. (Both groups got information about good sleep habits.) Oxygen treatment did improve the amount of oxygen in the blood. But it did not seem to improve blood pressure.

The second study included 181 obese people with sleep apnea. People were randomly divided into 3 treatment groups: CPAP, a weight-loss program or both. Blood pressure improved in all 3 groups. But the combination of CPAP and weight loss was linked to greater reductions than either treatment alone.

Those in the weight-loss program and those treated both with weight loss and CPAP had improvements in blood tests that measured metabolism. These improvements were not seen among those receiving only CPAP. C-reactive protein (CRP), a measure of inflammation in the body, improved in both weight-loss groups. Insulin levels and triglycerides (a fat linked to cardiovascular disease) also improved in the weight-loss groups.

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Study Reviews Marijuana Risks

Marijuana is becoming a legal drug in several states. Many people think marijuana is safe. However, this is not true. There are definite health hazards that come with marijuana use.

The New England Journal of Medicine published a review of these risks on June 5. Health hazards are much greater for people who begin use before age 21, because the brain is still developing during the teen years. Evidence suggests that effects on the brain from marijuana use by adolescents and teens can be permanent.

  • Addiction: Nine percent who experiment with marijuana become addicted. Among people who experiment as teenagers, one out of six later become addicted.
  • Withdrawal symptoms: After repeated use, there are symptoms that occur when you stop using marijuana. These include irritability, sleeping difficulties, depressed mood, cravings and anxiety.
  • Gateway drug concerns: Marijuana use can increase the risk of drug abuse and addiction later in life. Experts think this comes from changes in the brain's dopamine supply and related nerve pathways, which can be affected by using marijuana at an early age.
  • Abnormal brain development: This is a concern for people who smoke marijuana repeatedly when they are younger than 21. Brain scans show that repeated marijuana exposure leads to fewer brain cell connections in regions that control alertness, self-awareness, learning, memory, attentiveness and self control. These changes in brain anatomy are long lasting.
  • Schizophrenia: There is a higher chance of developing psychotic symptoms or schizophrenia if you have repeatedly smoked marijuana. People who have a family history of schizophrenia appear to have schizophrenia symptoms at an earlier age. And the symptoms are more severe if they have smoked marijuana.
  • Depression and anxiety: These problems are more common in people with a history of marijuana use.
  • Diminished lifetime achievement: Using marijuana is associated with lower income, greater need for public assistance, unemployment, criminal behavior, lower intelligence (IQ) test scores and lower life satisfaction. Not all of these can be blamed on marijuana. But it is clear that marijuana use interferes with school attendance and school performance, along with short- and long-term memory.
  • Motor vehicle accidents: Simulated (pretend) driving studies show that marijuana impairs drivers. Evidence suggests that if you have marijuana in your bloodstream, you are between three and seven times more likely to cause a motor vehicle accident compared with people who have not used the drug.
  • Chronic bronchitis: Cough and asthma-like symptoms are definitely more common in people who use marijuana.

The same paper indicates that several medical problems appear to benefit from marijuana. These include glaucoma, nausea, neuropathic pain, anorexia in AIDS patients, muscle spasticity in multiple sclerosis and some symptoms of rheumatoid arthritis and inflammatory bowel disease. The authors point out that marijuana is not as effective as other existing treatments for these problems. Because of the risks, the authors of this review conclude that marijuana has a very limited role for medical purposes.

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More News In Brief

  • Vaccine May Help Fight Pancreatic Cancer. The immune system fights infection. It also fights cancer. Some cancers don't attract the attention of our immune systems. They are especially lethal. If the immune system does not recognize a cancer cell as a problem, it will not target it and fight it. One of these hard-to-fight cancers is cancer of the pancreas. But researchers have developed a vaccine that might help the immune system to recognize and fight ductal adenocarcinoma, the most common kind of pancreatic cancer.

    The researchers published their work in Cancer Immunology Research on June 18. They tested the vaccine on 59 patients with this cancer. Surgery offers a chance of being cured. So most patients had surgery. It took place, on average, about 2 weeks after the vaccination. Doctors analyzed tumor samples from 39 patients. They compared these samples with samples from a group of unvaccinated patients. The findings show that most of the people who received the vaccine had clumps of lymphocytes (white blood cells from the immune system) closely intermixed with their tumor.

    Researchers are now hopeful that a cancer vaccine may be a new treatment option for pancreatic cancer. Additional work on the vaccine may lead to one  that generates an even more robust response from the immune system. This might help shrink pancreatic cancer tumors.

  • Veterans with Traumatic Brain Injury Have Higher Chance of Developing Dementia as They Age. An upsetting study in veterans has linked traumatic brain injury with a much higher risk for dementia later in life. This study, published June 25 in Neurology, looked at 188,784 veterans with an average age of 68. In order to enroll in the study, the participants could not have dementia. Researchers identified 1,229 veterans in the group who had suffered a traumatic brain injury (TBI) in the past. The study collected information for 7 years. During that time, 16% of the veterans with a previous TBI developed dementia, and only 10% of veterans without TBI developed dementia. This was a significant difference. Depression, post-traumatic stress disorder and a history of stroke appeared to add to the risk of developing dementia in patients with TBI history.
  • Computer Cracks Case of Mystery Infection. The June 19 issue of the New England Journal of Medicine reports a case involving a new use of technology that may revolutionize how infections are diagnosed. This technology is called "next generation sequencing" or "high-throughput sequencing." Currently, doctors must order specific blood or body fluid tests — one for each type of suspected infection — in order to confirm the presence of infections they suspect are causing symptoms. For common infections this process works fairly smoothly. For unusual infections, it may take several rounds of testing before a diagnosis is made. Sometimes, the tests give inaccurate results.

    This case report discussed a new way to test for infection. Blood and spinal fluid samples were processed and all genetic material that was present in the sample was catalogued. This was true whether it came from the human patient, or from bacteria or other infectious agents that were present in the fluid samples. Then, a computer subtracted out the genetic code that was human. Also by computer, the remaining genetic material was compared to a computerized library of DNA patterns from known infectious agents.

    Doctors at the University of California, San Francisco, used this technology to find the cause of a teenage boy's encephalitis (infection of the brain). They diagnosed him with a bacterial infection called leptospirosis. Up to this point, the cause of the infection was a mystery to doctors. This technology is likely to have a large role in diagnosing infectious diseases as it is further refined.

  • One-time Ultrasound Is Recommended for Most Older Men. An aortic aneurysm is a weakened and dilated area of the aorta, the largest artery of the body. The U.S. Preventive Services Task Force is recommending that all men ages 65 to 75 who have ever smoked should have a one-time ultrasound of the abdomen to check for this condition. Men who have never smoked may also benefit from a screening, if they have other risks for artery disease (for example, a family history of atherosclerosis).  The recommendation was released by the Annals of Internal Medicine on June 23. If an aneurysm is found, surgery can strengthen the artery. This can prevent a fatal artery rupture. The benefits of screening have not been shown for women who have a history of smoking.

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Mary Pickett, M.D., is an associate professor at Oregon Health Science University where she is a primary care doctor for adults. She supervises and educates residents in the field of Internal Medicine, for outpatient and hospital care. She is a lecturer for Harvard Medical School and a senior medical editor for Harvard Health Publications.


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