September 30th, 2008
You might have heard through the mainstream media or from friends about the chemical bisphenol-A or BPA. It’s a building block for common plastics and was commonly used to make those water bottles you carry around. It’s also found in can liners and dental sealants. In fact, it’s so common-7 billion pounds per year are produced worldwide-that major routes of exposure include dermal and inhalant, just touching it and breathing. Animal studies have shown BPA to be a weak estrogen agonist, that is it binds very weakly to, and therefore minimally activates, the estrogen receptor. Even though it’s a very weak estrogen agonist, it’s so common that it has been theorized that chronic, low-level exposure could lead to disease.
The Journal of the American Medical Association, JAMA for short, recently published an article looking at the association between BPA levels and common chronic illnesses. The study showed an association between elevated BPA levels and both diabetes and coronary artery disease. Other diseases such as cancer, arthritis, liver disease, asthma, stroke, and thyroid disease showed no association.
This study does have limitations. First, it only took a spot measurement of urinary BPA. This does not tell us what a person’s long term exposure looks like. Second, this was a population study and therefore can only show association, not causation. This is a very important distinction. The authors also note that this is the first study of its kind in humans and it will need to be independently replicated and prospective studies will need to be carried out as well.
Despite these limitations, there is certainly sufficient evidence to curtail exposure to BPA. Efforts are already underway to find suitable replacements and governments are placing restrictions on its production. This is a logical step until further longitudinal studies can prove whether BPA is truly harmful or not.
September 18th, 2008
I’ve seen a streak of bad nasal polyps this week. My guess is that I see 20 or so cases a year, but I’ve seen 4 in the last week or so. Seems like a good time to update the blog.
So what are nasal polyps? The word “polyps” conjures up some scary images for many people who associate it with pre-cancerous colon polyps. Nasal polyps are much different. First, they are not pre-cancerous in any way. They are growths of inflammatory tissue which arise from the lining of the nasal and sinus cavities. When you look at them under a microscope they contain sheets of cells called eosinophils, which are cells of the immune system that are commonly involved in allergic inflammation. The most common symptoms associated with nasal polyps are persistent nasal congestion and loss of sense of smell, called anosmia. Nasal polyps can lead to recurrent sinus infections if they grow enough to block the drainage pathways of the sinuses.
What causes nasal polyps? The true answer is: no one knows for sure. Nasal polyps are associated with allergies, but many polyp patients are non-allergic. Nasal polyps are often part of a syndrome called Samter’s Triad: nasal polyps, asthma, and sensitivity to medicines like aspirin, ibuprofen, or naprosyn.
How are nasal polyps treated? The mainstay of polyp treatment is surgical resection. Oral steroids will shrink polyps temporarily, but they come right back. Polyps also tend to recur following surgery, though how soon they recur is highly variable. In some people it’s a decade, in some people it’s a year or less. Most physicians agree that controlling any allergies that may be present is important to delay recurrence. This is usually done with immunotherapy or allergy shots. Nasal steroid sprays are also important in limiting recurrence. Some experts recommend aspirin desensitization, though this can be a dicey prospect in someone with aspirin induced wheezing. In the end, most cases of nasal polyps can be effectively managed by a team approach between allergists and otolaryngologists
September 10th, 2008
Here’s some exciting news about the flu shot. Researchers in Britain have developed a “universal” flu vaccine which could solve many of the issues with current flu vaccines. To understand this, a bit of background info on the influenza virus is necessary.
The influenza virus mutates at a very high rate. These mutations result in subtle changes in some of the viral components. You may have seen certain viral strains labeled with a code like H5N1 or H3N2. The letters H and N stand for components of the viral cell wall, hemagglutinin and neuraminidase if you must know, and the number tells us which strain of each component is present in the virus. Each year the vaccine manufacturers must guess which strains will hit the U.S. They do this by examining which strains are prevalent in Asia. They then pick two strains of influenza A (H1N1 and H3N2, most recently) to put into the vaccine. They also put influenza B in the vaccine, but it mutates much less so its strain remains relatively constant.
The proposed “universal” vaccine would utilize components inside the virus. These components are much more stable than the H and N components and therefore should provide protection against multiple different strains of the influenza virus. Manufacturers would no longer have to guess which strain to put in their vaccine.
It will take some time to prove that the new vaccine is effective and safe, but it could be in use in as little as 5 years. Let’s hope it works!
