Semin Hear 2015; 36(03): 175-196
DOI: 10.1055/s-0035-1555120
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Aging of the Human Vestibular System

Christopher K. Zalewski
1   Otolaryngology Branch, Audiology Unit, National Institute on Deafness and Other Communication Disorders (NIDCD), National Institutes of Health (NIH), Bethesda, Maryland
› Author Affiliations
Further Information

Publication History

Publication Date:
09 July 2015 (online)

Abstract

Aging affects every sensory system in the body, including the vestibular system. Although its impact is often difficult to quantify, the deleterious impact of aging on the vestibular system is serious both medically and economically. The deterioration of the vestibular sensory end organs has been known since the 1970s; however, the measurable impact from these anatomical changes remains elusive. Tests of vestibular function either fall short in their ability to quantify such anatomical deterioration, or they are insensitive to the associated physiologic decline and/or central compensatory mechanisms that accompany the vestibular aging process. When compared with healthy younger individuals, a paucity of subtle differences in test results has been reported in the healthy older population, and those differences are often observed only in response to nontraditional and/or more robust stimuli. In addition, the reported differences are often clinically insignificant insomuch that the recorded physiologic responses from the elderly often fall within the wide normative response ranges identified for normal healthy adults. The damaging economic impact of such vestibular sensory decline manifests itself in an exponential increase in geriatric dizziness and a subsequent higher prevalence of injurious falls. An estimated $10 to $20 billion dollar annual cost has been reported to be associated with falls-related injuries and is the sixth leading cause of death in the elderly population, with a 20% mortality rate. With an estimated 115% increase in the geriatric population over 65 years of age by the year 2050, the number of balanced-disordered patients with a declining vestibular system is certain to reach near epidemic proportions. An understanding of the effects of age on the vestibular system is imperative if clinicians are to better manage elderly patients with balance disorders, dizziness, and vestibular disease.

 
  • References

  • 1 Horak F. Role of the Vestibular System in Postural Control. 3rd ed. Philadelphia, PA: F.A. Davis Company; 2008
  • 2 Keshner E. Postural Abnormalities in vestibular Disorders. 3rd ed. Philadelphia, PA: F.A. Davis Company; 2007
  • 3 Peterka RJ. Sensorimotor integration in human postural control. J Neurophysiol 2002; 88 (3) 1097-1118
  • 4 Marchetti GF, Whitney SL. Older adults and balance dysfunction. Neurol Clin 2005; 23 (3) 785-805 , vii
  • 5 Shoair OA, Nyandege AN, Slattum PW. Medication-related dizziness in the older adult. Otolaryngol Clin North Am 2011; 44 (2) 455-471 , x
  • 6 Dewane JA. Dealing with dizziness and disequilibrium in older patients: a clinical approach. Topics in Geriatric Rehabilitation 1995; 11 (1) 30-38
  • 7 Cutson TM. Falls in the elderly. Am Fam Physician 1994; 49 (1) 149-156
  • 8 Hobeika CP. Equilibrium and balance in the elderly. Ear Nose Throat J 1999; 78 (8) 558-562 , 565–566
  • 9 Dillon CF, Gu Q, Hoffman HJ, Ko CW. Vision, hearing, balance, and sensory impairment in Americans aged 70 years and over: United States, 1999–2006. NCHS Data Brief 2010; 31: 1-8
  • 10 Katsarkas A. Dizziness in aging: a retrospective study of 1194 cases. Otolaryngol Head Neck Surg 1994; 110 (3) 296-301
  • 11 Baloh RW. Vestibular and auditory disorders. Curr Opin Neurol 1996; 9 (1) 32-36
  • 12 NIH. National Institutes of Deafness and Other Communication Disorders (NIDCD); 1997: 122
  • 13 University of Iowa Health Care. Comprehensive management of vestibular disorders. Currents 2002; 3 (2)
  • 14 Jacobson GP, McCaslin DL, Grantham SL, Piker EG. Significant vestibular system impairment is common in a cohort of elderly patients referred for assessment of falls risk. J Am Acad Audiol 2008; 19 (10) 799-807
  • 15 Kippenbrock T, Soja ME. Preventing falls in the elderly: Interviewing patients who have fallen. Researchers attempt to identify fall-risk factors from the patients' point of view. Geriatr Nurs (Minneap) 1993; 14 (4) 205-209
  • 16 Ambrose AF, Paul G, Hausdorff JM. Risk factors for falls among older adults: A review of the literature. Maturitas 2013; 75 (1) 51-61
  • 17 Todd CJ, Freeman CJ, Camilleri-Ferrante C , et al. Differences in mortality after fracture of hip: The east anglian audit. BMJ 1995; 310 (6984) 904-908
  • 18 Windmill IM, Freeman BA. Demand for audiology services: 30-yr projections and impact on academic programs. J Am Acad Audiol 2013; 24 (5) 407-416
  • 19 Matheson AJ, Darlington CL, Smith PF. Dizziness in the elderly and age-related degeneration of the vestibular system. N Z J Psychol 1999; 28 (1) 10-16
  • 20 Rosenhall U. Degenerative patterns in the aging human vestibular neuro-epithelia. Acta Otolaryngol 1973; 76 (2) 208-220
  • 21 Anniko M. The aging vestibular hair cell. Am J Otolaryngol 1983; 4 (3) 151-160
  • 22 Campos A, Canizares FJ, Sanchez-Quevedo MC, Romero PJ. Otoconial degeneration in the aged utricle and saccule. Adv Otorhinolaryngol 1990; 45: 143-153
  • 23 Furman JM, Redfern MS. Effect of aging on the otolith-ocular reflex. J Vestib Resl 2001; 11 (2) 91-103
  • 24 Lim DJ. Otoconia in health and disease. A review. Ann Otol Rhinol Laryngol Suppl 1984; 112: 17-24
  • 25 Maes L, Dhooge I, D'Haenens W , et al. The effect of age on the sinusoidal harmonic acceleration test, pseudorandom rotation test, velocity step test, caloric test, and vestibular-evoked myogenic potential test. Ear Hear 2010; 31 (1) 84-94
  • 26 Walther LE, Westhofen M. Presbyvertigo-aging of otoconia and vestibular sensory cells. Journal of vestibular research: equilibrium & orientation 2007; 17 (2–3) 89-92
  • 27 Rauch SD, Velazquez-Villasenor L, Dimitri PS, Merchant SN. Decreasing hair cell counts in aging humans. Ann N Y Acad Sci 2001; 942: 220-227
  • 28 Baloh RW, Jacobson KM, Socotch TM. The effect of aging on visual-vestibuloocular responses. Exp Brain Res 1993; 95 (3) 509-516
  • 29 Jang YS, Hwang CH, Shin JY, Bae WY, Kim LS. Age-related changes on the morphology of the otoconia. Laryngoscope 2006; 116 (6) 996-1001
  • 30 Matheson AJ, Darlington CL, Smith PF. Further evidence for age-related deficits in human postural function. J Vestib Res 1999; 9 (4) 261-264
  • 31 Rosenhall U, Rubin W. Degenerative changes in the human vestibular sensory epithelia. Acta Otolaryngol 1975; 79 (1–2) 67-80
  • 32 Richter E. Quantitative study of human scarpa's ganglion and vestibular sensory epithelia. Acta Otolaryngol 1980; 90 (3–4) 199-208
  • 33 Bergstrom B. Morphology of the vestibular nerve. I. Anatomical studies of the vestibular nerve in man. Acta Otolaryngol 1973; 76 (2) 162-172
  • 34 Bergstrom B. Morphology of the vestibular nerve. Ii. The number of myelinated vestibular nerve fibers in man at various ages. Acta Otolaryngol 1973; 76 (2) 173-179
  • 35 Lopez I, Honrubia V, Baloh RW. Aging and the human vestibular nucleus. J Vestib Res 1997; 7 (1) 77-85
  • 36 Alvarez JC, Diaz C, Suarez C , et al. Neuronal loss in human medial vestibular nucleus. Anat Rec 1998; 251 (4) 431-438
  • 37 Merchant SN, Velazquez-Villasenor L, Tsuji K, Glynn RJ, Wall III C, Rauch SD. Temporal bone studies of the human peripheral vestibular system. Normative vestibular hair cell data. Ann Otol Rhinol Laryngol Suppl 2000; 181: 3-13
  • 38 Velazquez-Villasenor L, Merchant SN, Tsuji K, Glynn RJ, Wall III C, Rauch SD. Temporal bone studies of the human peripheral vestibular system. Normative scarpa's ganglion cell data. Ann Otol Rhinol Laryngol Suppl 2000; 181: 14-19
  • 39 Engstrom H, Bergstrom B, Rosenhall U. Vestibular sensory epithelia. Arch Otolaryngol 1974; 100 (6) 411-418
  • 40 Igarashi M, Saito R, Mizukoshi K, Alford BR. Otoconia in young and elderly persons: A temporal bone study. Acta Otolaryngol Suppl 1993; 504: 26-29
  • 41 Johnsson LG. Degenerative changes and anomalies of the vestibular system in man. Laryngoscope 1971; 81 (10) 1682-1694
  • 42 Johnsson LG, Hawkins Jr JE. Otolithic membranes of the saccule and utricle in man. Science 1967; 157 (3795) 1454-1456
  • 43 Johnsson LG, Hawkins Jr JE. Vascular changes in the human inner ear associated with aging. Ann Otol Rhinol Laryngol 1972; 81 (3) 364-376
  • 44 Thalmann R, Ignatova E, Kachar B, Ornitz DM, Thalmann I. Development and maintenance of otoconia: Biochemical considerations. Ann N Y Acad Sci 2001; 942: 162-178
  • 45 Baloh RW, Honrubia V. Clinical neurophysiology of the vestibular system. 3rd ed. Philadelphia, PA: F.A. Davis Company; 2001
  • 46 Gretsy MA, Lempert T. Pathophysiology and clinical testing of otolith dysfunction. New York, NY: Karger; 2001
  • 47 Leigh RJ, Zee DS. The neurology of eye movements. 4th ed. New York: Oxford University Press; 2006
  • 48 Minor LB, Goldberg JM. Vestibular-nerve inputs to the vestibulo-ocular reflex: A functional-ablation study in the squirrel monkey. J Neurosci 1991; 11 (6) 1636-1648
  • 49 Tang PF, Woollacott M. Balance control in older adults. In: Bronstein AM, Brandt TW, , M., Nutt J. , eds. Clinical disorders of balance, posture and gait. 2nd ed. London: Arnold; 2004: 385-403
  • 50 Jacobson GP, McCaslin DL, Patel S, Barin K, Ramadan NM. Functional and anatomical correlates of impaired velocity storage. J Am Acad Audiol 2004; 15 (4) 324-333
  • 51 Mulch G, Petermann W. Influence of age on results of vestibular function tests. Review of literature and presentation of caloric test results. Ann Otol Rhinol Laryngol Suppl 1979; 88 (2 Pt 2 Suppl 56) 1-17
  • 52 Calder JH. Aging and the balance control systems. In: Weinstein BE, , ed. Geriatric audiology. New York, NY: Thieme; 2000: 141-167
  • 53 Lynch SJ, Nayak US, Isaacs B. Positional and optokinetic nystagmus in healthy old people. Age Ageing 1985; 14 (2) 122-124
  • 54 Kerber KA, Ishiyama GP, Baloh RW. A longitudinal study of oculomotor function in normal older people. Neurobiol Aging 2006; 27 (9) 1346-1353
  • 55 Irving EL, Steinbach MJ, Lillakas L, Babu RJ, Hutchings N. Horizontal saccade dynamics across the human life span. Invest Ophthalmol Vis Sci 2006; 47 (6) 2478-2484
  • 56 Peltsch A, Hemraj A, Garcia A, Munoz DP. Age-related trends in saccade characteristics among the elderly. Neurobiol Aging 2011; 32 (4) 669-679
  • 57 Tuunainen E, Poe D, Jantti P , et al. Presbyequilibrium in the oldest old, a combination of vestibular, oculomotor and postural deficits. Aging Clin Exp Res 2011; 23 (5–6) 364-371
  • 58 Sharpe JA, Sylvester TO. Effect of aging on horizontal smooth pursuit. Invest Ophthalmol Vis Sci 1978; 17 (5) 465-468
  • 59 Spooner JW, Sakala SM, Baloh RW. Effect of aging on eye tracking. Arch Neurol 1980; 37 (9) 575-576
  • 60 Jagacinski RJ, Liao MJ, Fayyad EA. Generalized slowing in sinusoidal tracking by older adults. Psychol Aging 1995; 10 (1) 8-19
  • 61 Morrow MJ, Sharpe JA. Smooth pursuit initiation in young and elderly subjects. Vision Res 1993; 33 (2) 203-210
  • 62 Kanayama R, Nakamura T, Sano R , et al. Effect of aging on smooth pursuit eye movement. Acta Otolaryngol Suppl 1994; 511: 131-134
  • 63 Kato I, Sakuma A, Ogino S, Takahashi K, Okada T. Aging effects upon pursuit eye movements. Acta Otolaryngol Suppl 1995; 520 ((Pt 2):) 293-294
  • 64 Simons B, Buttner U. The influence of age on optokinetic nystagmus. Eur Arch Psychiatry Neurol Sci 1985; 234 (6) 369-373
  • 65 Farooq SJ, Gottlob I, Benskin S, Proudlock FA. The effect of aging on torsional optokinetic nystagmus. Invest Ophthalmol Vis Sci 2008; 49 (2) 589-593
  • 66 Zackon DH, Sharpe JA. Smooth pursuit in senescence. Effects of target acceleration and velocity. Acta Otolaryngol 1987; 104 (3–4) 290-297
  • 67 Demer JL. Effect of aging on vertical visual tracking and visual-vestibular interaction. J Vestib Res 1994; 4 (5) 355-370
  • 68 Sharpe JA, Zackon DH. Senescent saccades. Effects of aging on their accuracy, latency and velocity. Acta Otolaryngol 1987; 104 (5–6) 422-428
  • 69 Pitt MC, Rawles JM. The value of measuring saccadic eye movement in the investigation of non-compressive myelopathy. J Neurol Neurosurg Psychiatry 1989; 52 (10) 1157-1161
  • 70 Paige GD. The aging vestibulo-ocular reflex (vor) and adaptive plasticity. Acta Otolaryngol Suppl 1991; 481: 297-300
  • 71 Paige GD. Senescence of human visual-vestibular interactions. 1. Vestibulo-ocular reflex and adaptive plasticity with aging. J Vestib Res 1992; 2 (2) 133-151
  • 72 Hajioff D, Barr-Hamilton RM, Colledge NR, Lewis SJ, Wilson JA. Re-evaluation of normative electronystagmography data in healthy ageing. Clin Otolaryngol Allied Sci 2000; 25 (4) 249-252
  • 73 Bruner A, Norris TW. Age-related changes in caloric nystagmus. Acta Otolaryngol Suppl 1971; 282: 1-24
  • 74 van der Laan FL, Oosterveld WJ. Age and vestibular function. Aerosp Med 1974; 45 (5) 540-547
  • 75 Clement PA, Van der Laan FL, Oosterveld WJ. The influence of age on vestibular function. Acta Otorhinolaryngol Belg 1975; 29 (1) 163-172
  • 76 Karlsen EA, Hassanein RM, Goetzinger CP. The effects of age, sex, hearing loss and water temperature on caloric nystagmus. Laryngoscope 1981; 91 (4) 620-627
  • 77 Ghosh P. Aging and auditory vestibular response. Ear Nose Throat 1985; 64 (5) 264-266
  • 78 Jacobson GP, Henry KG. Effect of temperature on fixation suppression ability in normal subjects: The need for temperature- and age-dependent normal values. Ann Otol Rhinol Laryngol 1989; 98 (5 Pt 1): 369-372
  • 79 Peterka RJ, Black FO, Schoenhoff MB. Age-related changes in human vestibulo-ocular reflexes: Sinusoidal rotation and caloric tests. J Vestib Res 1990; 1 (1) 49-59
  • 80 Mallinson AI, Longridge NS. Caloric response does not decline with age. J Vestib Res 2004; 14 (5) 393-396
  • 81 Davidson J, Wright G, McIlmoyl L, Canter RJ, Barber HO. The reproducibility of caloric tests of vestibular function in young and old subjects. Acta Otolaryngol 1988; 106 (3–4) 264-268
  • 82 Wall III C, Black FO. Intersubject variability in vor responses to 0.005–1.0 hz sinusoidal rotations. Acta Otolaryngol Suppl 1984; 406: 194-198
  • 83 Wall III C, Black FO, Hunt AE. Effects of age, sex and stimulus parameters upon vestibulo-ocular responses to sinusoidal rotation. Acta Otolaryngol 1984; 98 (3–4) 270-278
  • 84 Enrietto JA, Jacobson KM, Baloh RW. Aging effects on auditory and vestibular responses: A longitudinal study. Am J Otolaryngol 1999; 20 (6) 371-378
  • 85 Tian JR, Crane BT, Wiest G, Demer JL. Effect of aging on the human initial interaural linear vestibulo-ocular reflex. Exp Brain Res 2002; 145 (2) 142-149
  • 86 Serrador JM, Lipsitz LA, Gopalakrishnan GS, Black FO, Wood SJ. Loss of otolith function with age is associated with increased postural sway measures. Neurosci Lett 2009; 465 (1) 10-15
  • 87 Maki BE, Holliday PJ, Topper AK. A prospective study of postural balance and risk of falling in an ambulatory and independent elderly population. J Gerontol 1994; 49 (2) M72-M84
  • 88 Chang NY, Hiss MM, Sanders MC , et al. Vestibular perception and the vestibulo-ocular reflex in young and older adults. Ear Hear 2014; 35 (5) 565-570
  • 89 Roditi RE, Crane BT. Suprathreshold asymmetries in human motion perception. Exp Brain Res 2012; 219 (3) 369-379
  • 90 Roditi RE, Crane BT. Directional asymmetries and age effects in human self-motion perception. Journal of the Association for Research in Otolaryngology: JARO. 2012; 13 (3) 381-401
  • 91 Akin FW, Murnane OD, Tampas JW, Clinard CG. The effect of age on the vestibular evoked myogenic potential and sternocleidomastoid muscle tonic electromyogram level. Ear Hear 2011; 32 (5) 617-622
  • 92 Brantberg K, Granath K, Schart N. Age-related changes in vestibular evoked myogenic potentials. Audiol Neurootol 2007; 12 (4) 247-253
  • 93 Lee SK, Cha CI, Jung TS, Park DC, Yeo SG. Age-related differences in parameters of vestibular evoked myogenic potentials. Acta Otolaryngol 2008; 128 (1) 66-72
  • 94 Su HC, Huang TW, Young YH, Cheng PW. Aging effect on vestibular evoked myogenic potential. Otology & neurotology: official publication of the American Otological Society, American Neurotology Society. [and] European Academy of Otology and Neurotology 2004; 25 (6) 977-980
  • 95 Welgampola MS, Colebatch JG. Vestibulocollic reflexes: Normal values and the effect of age. Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology. 2001; 112 (11) 1971-1979
  • 96 Zapala DA, Brey RH. Clinical experience with the vestibular evoked myogenic potential. J Am Acad Audiol 2004; 15 (3) 198-215
  • 97 Janky KL, Shepard N. Vestibular evoked myogenic potential (vemp) testing: Normative threshold response curves and effects of age. J Am Acad Audiol 2009; 20 (8) 514-522
  • 98 Agrawal Y, Zuniga MG, Davalos-Bichara M , et al. Decline in semicircular canal and otolith function with age. Otology & neurotology: official publication of the American Otological Society, American Neurotology Society. [and] European Academy of Otology and Neurotology 2012; 33 (5) 832-839
  • 99 Iwasaki S, Smulders YE, Burgess AM , et al. Ocular vestibular evoked myogenic potentials to bone conducted vibration of the midline forehead at fz in healthy subjects. Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology. 2008; 119 (9) 2135-2147
  • 100 Rosengren SM, Govender S, Colebatch JG. Ocular and cervical vestibular evoked myogenic potentials produced by air- and bone-conducted stimuli: Comparative properties and effects of age. Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology. 2011; 122 (11) 2282-2289
  • 101 Piker EG, Jacobson GP, McCaslin DL, Hood LJ. Normal characteristics of the ocular vestibular evoked myogenic potential. J Am Acad Audiol 2011; 22 (4) 222-230
  • 102 Nguyen KD, Welgampola MS, Carey JP. Test-retest reliability and age-related characteristics of the ocular and cervical vestibular evoked myogenic potential tests. Otol Neurotol 2010; 31 (5) 793-802
  • 103 Tseng CL, Chou CH, Young YH. Aging effect on the ocular vestibular-evoked myogenic potentials. Otol Neurotol 2010; 31 (6) 959-963
  • 104 Piker EG, Jacobson GP, Burkard RF, McCaslin DL, Hood LJ. Effects of age on the tuning of the cvemp and ovemp. Ear Hear 2013; 34 (6) e65-e73
  • 105 Chamberlain W. Restriction in upward gaze with advancing age. Am J Ophthalmol 1971; 71 (1 Pt 2): 341-346
  • 106 Agrawal Y, Schubert MC, Migliaccio AA , et al. Evaluation of quantitative head impulse testing using search coils versus video-oculography in older individuals. Otol Neurotol 2014; 35 (2) 283-288
  • 107 Davalos-Bichara M, Agrawal Y. Normative results of healthy older adults on standard clinical vestibular tests. Otol Neurotol 2014; 35 (2) 297-300
  • 108 Matino-Soler E, Esteller-More E, Martin-Sanchez JC, Martinez-Sanchez JM, Perez-Fernandez N. Normative data on angular vestibulo-ocular responses in the yaw axis measured using the video head impulse test. Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology. 2014
  • 109 Li C, Layman AJ, Geary R , et al. Epidemiology of vestibulo-ocular reflex function: Data from the baltimore longitudinal study of aging. Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology. 2014
  • 110 McCaslin DL, Jacobson GP, Bennett ML, Gruenwald JM, Green AP. Predictive properties of the video head impulse test: Measures of caloric symmetry and self-report dizziness handicap. Ear Hear 2014; 35 (5) e185-e191
  • 111 Hirvonen TP, Aalto H, Pyykko I, Juhola M, Jantti P. Changes in vestibulo-ocular reflex of elderly people. Acta Otolaryngol Suppl 1997; 529: 108-110
  • 112 Hsieh LC, Lin HC, Lee GS. Aging of vestibular function evaluated using correlational vestibular autorotation test. Clin Interv Aging 2014; 9: 1463-1469
  • 113 Guyot JP, Psillas G. Test-retest reliability of vestibular autorotation testing in healthy subjects. Otolaryngology–head and neck surgery: official journal of American Academy of Otolaryngology-. Head Neck Surg 1997; 117 (6) 704-707
  • 114 Blatt PJ, Schubert MC, Roach KE, Tusa RJ. The reliability of the vestibular autorotation test (vat) in patients with dizziness. J Neurol Phys Ther 2008; 32 (2) 70-79
  • 115 Li CW, Hooper RE, Cousins VC. Sinusoidal harmonic acceleration testing in normal humans. Laryngoscope 1991; 101 (2) 192-196
  • 116 Stefansson S, Imoto T. Age-related changes in optokinetic and rotational tests. Am J Otol 1986; 7 (3) 193-196
  • 117 DiZio P, Lackner JR. Age differences in oculomotor responses to step changes in body velocity and visual surround velocity. J Gerontol 1990; 45 (3) M89-M94
  • 118 Zapala DA, Olsholt KF, Lundy LB. A comparison of water and air caloric responses and their ability to distinguish between patients with normal and impaired ears. Ear Hear 2008; 29 (4) 585-600
  • 119 Ochi K, Ohashi T. Age-related changes in the vestibular-evoked myogenic potentials. Otolaryngology–head and neck surgery: official journal of American Academy of Otolaryngology-. Head Neck Surg 2003; 129 (6) 655-659
  • 120 Basta D, Todt I, Ernst A. Normative data for p1/n1-latencies of vestibular evoked myogenic potentials induced by air- or bone-conducted tone bursts. Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 2005; 116 (9) 2216-2219
  • 121 Basta D, Todt I, Ernst A. Characterization of age-related changes in vestibular evoked myogenic potentials. J Vestib Res 2007; 17 (2–3) 93-98
  • 122 Tinetti ME, Williams CS, Gill TM. Dizziness among older adults: A possible geriatric syndrome. Ann Intern Med 2000; 132 (5) 337-344