This week, Dr. Sydney Spiesel discusses the puzzling and unwelcome results of a big diabetes study, a controversial claim that some HIV patients don't pose a risk of passing along their infection, and the plausibility of a link between smoking pot and getting gum disease.
Problem: The medical world was shaken last week by the premature interruption of an important experiment in progress. The ACCORD study, which had been running for four years, hypothesized that if patients with the most common form of diabetes were treated more rigorously, they would experience fewer of the complications of this disease, like strokes and heart attacks. Contrary to expectations, one of the interventions—keeping the patient's blood sugar under rigorous control—was associated with a higher, rather than lower, death rate, so that part of the study was abruptly stopped.
Condition: Diabetes comes in two forms, both characterized by excessive blood levels of glucose, a simple sugar central to our energy metabolism. In type 1 diabetes, the insulin-producing cells fail, so no insulin is available to allow body cells to take up blood sugar. In type 2 diabetes, the insulin-controlled "gates" that allow the entry of sugar into cells gradually lose their sensitivity, so that more and more insulin is needed to control blood sugar.
Findings: The first goal of treatment for both forms of diabetes, then, is good blood sugar control. In a previous important American study, tight control of blood sugar in type 1 diabetics showed clear cardiovascular benefits. Remarkably, these benefits continued for many years even after patients relaxed the blood sugar controls. Another large and important study of the effects of blood sugar control on type 2 diabetics in Britain showed a substantial reduction in most complications, though little or no cardiovascular effect. A few earlier and much smaller studies suggested that blood sugar control for type 2 diabetics might have harmful cardiovascular consequences, but the results of the large British study were very reassuring on that score. That's why the ACCORD results were so shocking.
Conclusion (or lack thereof): Alas, we will probably be grasping for an explanation for some time. The cardiovascular problems showed up while the study was ongoing and still await detailed consideration. That is still probably a year or two away. I wish I could offer even a speculative answer, but until more details are released, I, too, am in the dark.
Question: Controversy is also rocking the world of HIV/AIDS. It began when four leading and highly respected HIV experts in Switzerland, writing on behalf of the Swiss Federal Commission for HIV/AIDS, produced a consensus statement asserting that some HIV-infected people pose essentially no risk of passing the infection to their sexual partners. Even without a condom, these experts argue, the risk of transmission is less than one in 100,000.
New report: The Swiss experts argue that the danger of transmission is vanishingly small only if the following conditions are met: 1) An HIV-infected patient is receiving effective antiviral treatment (as demonstrated by undetectable levels of HIV viral RNA for at least six months); 2) the patient adheres to treatment under the close supervision of a doctor; and 3) has no other sexually transmitted infections
Evidence: In favor of their position, the authors cite a number of studies that demonstrate that HIV infection is closely correlated with viral load in blood and genital secretions, and that treatment with highly active antiretroviral therapy can bring those viral loads to below detectable levels. They add some warnings: In the beginning phase of HIV infections, patients are typically highly infectious. And if they stop antiviral treatment, their viral load usually rises rapidly. There is a known case of HIV transmission occurring during such a period.
Counterpoint: The consensus statement is diametrically opposed to the advice usually given to HIV-infected people, and its release caused a furor. For example, UNAIDS and the World Health Organization jointly rejected the Swiss position, as did the Centers for Disease Control in the United States. Their position is that while the risk might indeed be low, that is still not proven, and so their prevention recommendations, which include condom use, should be continued. There is substantial concern that patients will misread the Swiss position and ignore "safer sex" recommendations in circumstances that don't satisfy the stringent criteria suggested by the authors of the consensus paper. There is also concern that in much of the world, those conditions can never be met: It would be impossible for patients to get closely supervised treatment, the needed medications, to be checked for other sexually transmitted infections, and to be tested frequently so that they can be sure their viral load remains undetectably low.
Conclusion: I suspect that the resolution of this dispute will emerge in time, but not from a program of organized research. Instead, some HIV-positive patients will behave like many HIV-negative people and forget about safer-sex recommendations. And then—for better or worse—we will learn about the true risk of HIV transmission in an age of increasingly effective treatment. I actually suspect that the Swiss will turn out to be right, but their stance still makes me nervous.
Problem: As your dentist will be glad to tell you, periodontal disease—inflammation of the gum tissue—is common and quite harmful. If it is untreated, the teeth surrounded by the sick gum tissue will loosen and may fall out. Many things contribute: poor dental hygiene at home and excess plaque, inadequate professional dental care, chronic diseases like diabetes, and tobacco smoke. What about marijuana?
Study: New research conducted in New Zealand suggests a link between weed and gum disease. The researchers followed a cohort of about 1,000 people beginning when they were 3 years old. The group was surveyed at various ages for socioeconomic status, tobacco and marijuana use, and frequency of professional dental care (though not for tooth brushing or for other drug use). At ages 26 and 32, with more than 90 percent of the original cohort still enrolled, the group was examined for periodontal disease.
Findings: Low socioeconomic status, poor professional dental care, and tobacco smoking were all highly associated with periodontal disease. This confirmed previous findings. But for the first time, so was marijuana smoking. The four factors were also strongly associated with each other (poor people were much more likely than wealthier ones to get bad dental care and to smoke tobacco and marijuana). So, the researchers used regression analysis to clarify the role of marijuana use separate from the other factors. They found strong support for an independent association—absent poverty, lack of dental care, and tobacco—between smoking pot and getting gum disease.
Caveat 1: This evidence, though, is far from definitive. First of all, the absence of information about daily dental hygiene and—much more significantly—other drug use is a serious flaw in the study's design. Cocaine and methamphetamine use are both highly associated with periodontal disease. Cocaine is expensive in New Zealand and apparently not much used there, but methamphetamine is said to be widely available. One can only speculate about whether stoners' meth use contributed to the observed prevalence of periodontal disease.
Caveat 2: The authors of this study also don't inspire confidence because they slide from association to causation. In one sentence, they go from "a strong association between cannabis use and periodontitis" to an indication that "long-term smoking of cannabis is detrimental to the periodontal tissues" and then conclude that "public health measures to reduce the prevalence of cannabis smoking may have periodontal benefits for the population." This unwarranted leap from inference to inference clouds instead of illuminates.
Conclusion: Which, alas, leaves me with no useful information on the subject of marijuana use and gum disease to pass on to my patients.
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