Clinical Briefs
By Louis Kuritzky, MD, Clinical Assistant Professor, University of Florida, Gainesville
Dr. Kuritzky is a retained consultant for Boehringer Ingelheim, Daiichi Sankyo, Forest Pharmaceuticals,
Janssen, Lilly, Novo Nordisk, Pfizer, and Sanofi.
Vitamin D Status: Does Ethnicity Matter?
Source: Powe CE, et al. N Engl J Med 2013;369:1991-2000.
Interest in vitamin d has been spurred by the observation that low 25-hydroxyvitamin D levels (25[OH]D) are associated not only with risk for osteoporosis and fracture, but also with risk for falls in seniors. Indeed, limited data suggest that supplementation of low vitamin D in frail seniors reduces falls. There is, however, some disconnect between 25(OH)D levels as determined in black vs white Americans. That is, black Americans have lower 25(OH)D levels than whites, yet blacks have both a higher bone mineral density and lower risk for osteoporotic fracture.
Current clinical practice does not typically include measurement of vitamin D-binding protein, which is the primary plasma protein carrying vitamin D in the blood, accounting for 85-90% of circulating vitamin D. Similar to the biochemistry of testosterone, it appears to be only the free 25(OH)D fraction (i.e., not bound to vitamin D-binding protein) that is active at tissue target sites. Genetic polymorphisms are responsible for variations in levels of vitamin D-binding protein, and hence the amount of bioavailable vitamin D.
Powe et al compared bioavailable vitamin D levels in subjects participating in the Healthy Aging in Neighborhoods of Diversity Across the Life Span Study (n = 2085). Overall, blacks had substantially lower 25(OH)D levels than whites (16 ng/mL vs 26 ng/mL). Similarly, levels of vitamin D-binding protein were essentially twice as high in white vs black subjects (337 mcg/mL vs 168 mcg/mL). Genetic polymorphisms more commonly seen in black Americans than whites — not ethnicity itself — explained approximately 80% of the differences in vitamin D-binding protein levels.
The greater bioavailable vitamin D in blacks compared to whites at comparable 25(OH)D levels explains most of the above-mentioned discrepant black/white fracture risk. Additionally, since polymorphisms associated with increased bioavailable vitamin D can be seen in diverse ethnicities, the authors suggest that we may soon need to be incorporating measurement of vitamin D-binding protein to accurately interpret vitamin D status.
40 Bazillion Squirrels Can't Be Wrong: Eat Your Nuts
Source: Bao Y, et al. N Engl J Med 2013; 369:2001-2011.
At least in my neck of the woods, the common acorn (AKA: oak nut) is the preferred cuisine of squirrels. And have you ever seen an unhealthy, obese, diabetic, or hypertensive squirrel? Although across-traffic road misadventure while seeking nuts may be a common cause of death, the species enjoys unabated proliferation in the southeast.
Previous literature has established a favorable inverse relationship between nut consumption and the incidence of cardiovascular disease and diabetes. Whether this association translates into improved mortality as well has not been established. Bao et al report on mortality in subjects participating in the Nurses' Health Study (n = 76,464 women) and the Health Professionals Follow-up Study (n = 42,498 men) in relation to nut consumption.
After adjustment for other risk factors, there was a statistically significant linear inverse relationship between frequency of nut consumption and mortality in both men and women ranging from a 7% mortality reduction associated with nut consumption less than once a week up to a 20% mortality reduction associated with daily nut consumption. And by the way, it wasn't just the high-ticket item nuts like cashews; the relationships held for simple peanuts as well.
Despite their dietary wisdom, grey squirrels only live an average of 6 years. So, the moral of the story is that nuts can help you live longer, as long as you also look both ways before crossing the street and don't stop in the middle.
Tinnitus: Not Much Room for Optimism
Source: Gabuley D, et al. Lancet 2013; 382:1600-1607.
The consequences of tinnitus (tin) range from nuisance distraction to catastrophic. Some individuals quickly learn to ignore the spontaneous auditory sensations, but others are plagued with relentless awareness of competing, sometimes noxious sounds. The unfortunate "bottom line" conclusion of the authors of this article is that there are no proven effective pharmacotherapeutic treatments for TIN. Since epidemiologic surveys in Europe and North America conclude that TIN may affect as many as 10% of adults, there is a compelling need to identify effective interventions.
There is no test that proves the diagnosis of TIN. Rather, it is a subjective report. Investigation for CNS pathology (MRI) is suggested when TIN is not symmetric in both ears, when audiometry indicates unilateral abnormality, if there is asymmetric hearing loss, or if there are positive neurologic findings. One special group — patients with TIN that is pulsatile and synchronous with heartbeat — requires even more detailed investigation.
TIN is associated with depression and anxiety, each of which potentially merits treatment in its own right. Treatment specific to TIN is generally based on sound generators, of which there are a great variety, and for which outcome data are sparse.
Uncommonly, TIN may be remedied when it is associated with an ototoxic medication or simple mechanical cerumen impaction. Some patients report meaningful benefits from the combination of sound-generation devices and cognitive behavioral therapy. Evolving treatments that involve magnetic brain stimulation show some promise. Highly effective treatments to reduce or resolve TIN remain elusive.
