Information about the prevalence of balance problems has been limited, although it has been recognized that balance disorders, disequilibrium and dizziness from vestibular disturbance constitute a major public health problem. Epidemiologists and other staff of NIDCD have collaborated with the National Center for Health Statistics (NCHS) on the development of questions and examinations for the assessment of balance problems in the U.S. population. For example, we suggested questions for the 1994 and 1995 Disability Supplement (DS) to the National Health Interview Survey (NHIS) with regard to chronic (3+ months) problems with balance and/or dizziness. Based on these data, we estimate 6.2 million Americans have chronic balance or dizziness problems. As with other sensory functions, the prevalence increases greatly with age: 1.9% at ages 25-44 years, 3.7% at 45-64 years, and 9.1% at 65 years or more. Using multivariable logistic regression analysis, we found that chronic balance problems were associated with several factors, including tinnitus (odds ratio = 5.0; 95% confidence interval: 4.4, 5.6), activity limitations (4.8; 4.4, 5.3), depression and anxiety (3.3; 3.0, 3.7), vision trouble (2.4; 2.1, 2.7), hearing trouble (1.7; 1.5, 1.9), female sex (1.25; 1.15, 1.35) and age. Age effects decreased after inclusion of several age-related conditions, but remained significant. In addition to the DS, we have collaborated with NCHS on the design of a balance component for the Fourth National Health and Nutrition Examination Survey (NHANES IV), 1999-2004. This survey began collecting household questionnaires and conducting examinations in April 1999. A modified Romberg test is being used in the mobile examination centers (MECs) to provide an objective measure of the subjects' balance/vestibular performance. Also, questionnaires relating to problems with balance, dizziness and falls are completed during household interviews conducted prior to the examination in the MEC. Similarly, our knowledge of disorders of the chemical senses has been quite limited. A large, nonrandom survey conducted by the National Geographic Society in 1987 found that 1% of their 1.2 million respondents could not smell three or more of six odorants using a """"""""scratch and sniff"""""""" test. Age was an important factor, with a decline beginning in the second decade of life. No comparable data has been available for taste, although it has been suggested that the sense of taste remains more robust with age. Using the DS to the NHIS, we estimate that 2.7 million (1.4%) adults in the U.S. have a chronic olfactory (sense of smell) problem. In addition, we found 1.1 million (0.6%) adults in the U.S. had a chronic gustatory (taste) problem. When smell or taste problems were combined, 3.2 million (1.65%) adults in the U.S. were estimated to have a chronic chemosensory problem. The estimated prevalence rates increase markedly with age. Almost 40% of adults with a chemosensory problem (1.5 million) were 65 or more years of age. In a multivariate analysis, we found overall health status, other sensory impairments, functional limitations (including difficulty standing or bending), depression, phobia, and several other health-related characteristics were associated with an increase in chemosensory problems. In addition, we have analyzed data obtained through a collaboration with researchers at Yale University on the perceived strength of tastes of sour, bitter, salt, and sweet for subjects with or without the genetic trait of tasting PROP (6-n-propylthiouracil). All four taste qualities were studied using both magnitude matching and the labeled magnitude scale (LMS). We presented our findings at the annual meeting of the Association for Chemoreception Sciences. Tasters and especially supertasters of PROP differ from nontasters in their liking of each of the four basic taste qualities using either psychophysical measurement approach, which has implications for food preferences and some clinical complaints.
