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   Olfactory Decline May Identify Prodromal Dementia in Blacks, Whites    
      
      
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   Olfactory Decline May Identify Prodromal Dementia in Blacks, Whites    
      
   Samson, Kurt    
      
   Neurology Today:    
   16 February 2017 - Volume 17 - Issue 4 - p 8–11    
   doi: 10.1097/01.NT.0000513249.54961.fc    
   Features    
   Back to Top | Article Outline    
   ARTICLE IN BRIEF    
   The first long-term study to link olfactory deficits and dementia in elderly   
   black and white individuals found that white men and women with poorer   
   olfactory identification scores had a threefold greater risk of dementia over   
   a 12-year study period,    
   while black subjects had a twofold increased risk.    
      
   Increased inability to identify smells is recognized as a potential marker of   
   neurodegeneration and Alzheimer's disease (AD) dementia in older white   
   individuals, but the same also holds true to a lesser extent in black men and   
   women, according to a study    
   published in the December 30, 2016 online edition of Neurology.    
      
   When adjusted for race, demographics, other medical comorbidities, and   
   lifestyle factors, the investigators discovered that white men and women with   
   poorer olfactory identification (OI) scores had a threefold greater risk of   
   dementia over a 12-year study    
   period, while black subjects had a twofold increased risk.    
      
   This is the first long-term study to link olfactory deficits and dementia in   
   elderly black and white individuals; most studies have included only white   
   subjects, said lead author Kristine Yaffe, MD, professor of psychiatry,   
   neurology and epidemiology at    
   the University of California, San Francisco.    
      
   The olfactory system undergoes structural and functional changes in the early   
   stage of AD, and olfactory dysfunction is recognized as one of the earliest   
   and most common symptoms of neurodegenerative disease, Dr. Yaffe explained.   
   Testing the olfactory    
   bulb for proteins that cause AD-related degenerative processes may one day be   
   a way to test for the disease. Olfactory bulb concentrations of tau,   
   amyloid-beta, and alpha-synuclein significantly increase with the Braak   
   stages, and their pathology can    
   reflect the degree of pathologies in other regions of the brain.    
      
   Studies have also shown greater OI deficits in AD patients compared to those   
   with vascular dementia, and that the site of vascular pathology may determine   
   the type and severity of olfactory dysfunction, said Dr. Yaffe.    
      
   “Previous findings have shown that differences in OI decline between older   
   whites and blacks, with blacks having significantly worse olfactory   
   function,” she said. “What's happening here appears to be degeneration of   
   the olfactory nerves in advance    
   of symptoms of dementia in certain people.”    
      
   “This suggests that it might be possible to test for dementia risk before   
   any symptoms appear, like a window on the brain. Once we have good   
   disease-modifying agents, this could help doctors target treatment.”    
      
   Back to Top | Article Outline    
   METHODS, RESULTS    
   In the new study, Dr. Yaffe and her team studied the association in 2,428   
   older black and white adults between the ages of 70 and 79 years —   
   participants in the Health, Aging and Body Composition (Health ABC) study.   
   None had dementia at the study's    
   outset. Odor identification was assessed in the third year using the Cross   
   Cultural Smell Identification Test (B-SIT), while global cognition was   
   evaluated repeatedly using the Modified Mini-Mental Status Examination (3MS).    
      
   After initial evaluation the subjects were followed for 12 years, with   
   dementia determined using records of hospitalization, dementia prescriptions,   
   or a 1.2 standard decline in race-stratified global cognition score.    
      
   Whites with poor or moderate OI had the greater risk of dementia (adjusted HR   
   = 3.34) compared to those with good OI. In the black cohort, worse OI was also   
   associated with increased risk of dementia, although the magnitude was weaker.   
   In poor OI    
   subjects the adjusted hazard ratio was 2.03 while it was 1.42 in the moderate   
   group. The researchers found no interaction between OI and apolipoprotein E4   
   and risk of dementia.    
      
   Among whites, 33.8 percent of participants with poor OI developed dementia   
   compared with 10.2 percent of those with good OI. Among blacks, 31.9 percent   
   of participants with poor OI developed dementia versus 17.7 percent with high   
   OI.    
      
   Those blacks with moderate OI had an approximately 50 percent increased risk   
   of dementia in unadjusted models. When adjusted for possible confounders, poor   
   OI remained associated with increased dementia risk (HR = 2.03), but moderate   
   scores were only    
   marginally associated.    
      
   Among white participants, older age, lower education and literacy, having an   
   apolipoprotein E4 (APOE4) allele, current smoking, and lower body mass index   
   (BMI) were significantly associated with poor OI. A similar pattern was   
   observed among older black    
   participants, with lower education and literacy, as well as lower BMI,   
   significantly associated with poor OI. In contrast, among black participants,   
   not having an APOE4 allele was associated with worse OI scores, the   
   researchers found.    
      
   “We don't know why the effect we found was not as strong in black subjects,   
   but one theory is that blacks tend to be more vulnerable to vascular dementia   
   versus AD than do whites,” said Dr. Yaffe, who is also chief of geriatric   
   psychiatry and    
   director of the Memory Disorders Clinic at San Francisco Veterans Affairs   
   Medical Center.    
      
   Unlike most current biomarkers, olfactory testing represents a candidate for   
   widespread utility, she said. “This is a small standardized test that is   
   already available, but I am not aware that it is being used anywhere for   
   evaluating dementia risk.”    
      
   Figure. DR. KRISTINE...    
   Figure. DR. KRISTINE...    
      
   The researchers will next be looking at the test in older adults with   
   traumatic brain injury, she told Neurology Today.    
      
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