By Marcello Cherchi, MD PhD
For patients
When a patient begins to have problems thinking (such as with Alzheimer’s disease or other dementias), they (or their family) may notice problems with equilibrium as well. It is usually not clear whether the “thinking” problem causes the equilibrium problem. Your doctor may check several tests of balance to see whether there is some other disease causing disequilibrium. A cognitive neurologist may treat the “thinking” problem, while the balance specialist may refer you for vestibular rehabilitation therapy and a home assessment (usually done by an occupational therapist) to make you safer and less likely to fall.
For clinicians
Overview
Cognition and maintenance of equilibrium are complex, multi-faceted processes, which makes their interrelationship challenging to study. Research on this relationship often reaches conflicting conclusions, though this is probably at least in part because of the different diagnostic criteria and different outcome measures employed. It has not been clearly established that cognitive impairment causes disequilibrium, but there are several potential mechanisms by which such a relationship could hold, including impairment in visuo-spatial abilities, attention, executive function, judgement and ability to navigate around obstacles, and reduced response times. When a patient with diagnosed cognitive impairment (of whatever type) is referred to an otoneurologist or neuro-otologist to be evaluated for disequilibrium, it is reasonable to undertake a workup to look for common primary vestibular diseases. If such workup does not reveal another cause, then it is medically reasonable to use cognitive impairment as a provisional explanation for the disequilibrium. A cognitive neurologist usually manages the cognitive impairment, and the vestibular clinician may refer the patient for vestibular rehabilitation therapy, as well as a home safety assessment (usually by an occupational therapist) to reduce the risks of falls and injuries.
Introduction
The relationship between cognitive impairment and disequilibrium is challenging to study for numerous reasons, not the least of which include:
- Cognition is a complex process, and different studies use different measures of cognition when examining the relationship with equilibrium. Some studies use what are thought to be discrete cognitive diagnoses (such as mild cognitive impairment, Alzheimer’s disease, Pick’s dementia, etc.), while others focus on the results of more circumscribed cognitive assessments (such as visuo-spatial abilities (Lee et al. 2020), executive function (Ambrose et al. 2013; Muir et al. 2012; Taylor et al. 2018) or attention (Ambrose et al. 2013)).
- Maintenance of equilibrium is a complex process, and different studies use different measures of equilibrium when examining the relationship with cognitive impairment. Some studies measure gait parameters (Allali et al. 2016; Bahureksa et al. 2017; Bridenbaugh and Kressig 2014; Doi et al. 2015; Kang et al. 2020), others use falls (Allali et al. 2017; Ambrose et al. 2013; Chantanachai et al. 2021; Delbaere et al. 2012; Doi et al. 2015; Kuan et al. 2021; Lee et al. 2020; Leroy et al. 2023; Liang et al. 2023; Muir et al. 2012; Seijo-Martinez et al. 2016; Tyrovolas et al. 2016; Zhang et al. 2021; Zhou et al. 2022), others use subjective measures (such as the Dizziness Handicap Inventory (Lee et al. 2020)), etc.
Probably most studies report at least an association between cognitive impairment and falls (Ambrose et al. 2013; Delbaere et al. 2012; Doi et al. 2015; Kuan et al. 2021; Liang et al. 2023; Tyrovolas et al. 2016; Zhang et al. 2021).
In contrast, other research reports no clear association between cognitive impairment and falls (Chantanachai et al. 2021; Lee et al. 2020; Leroy et al. 2023; Seijo-Martinez et al. 2016), with some studies concluding that “global” measures of cognition bear no clear relationship to fall risk (Chantanachai et al. 2021; Lee et al. 2020).
However, even some of those studies (disputing any correlation between measures of global cognition and fall risk) note that deficits specific cognitive domains, such as visuospatial abilities (Lee et al. 2020), do correlate with fall risk.
More nuanced studies note that the relationship between cognitive impairment and falls varies depending on the type and degree of cognitive impairment (Allali et al. 2017) and on other demographic factors (Zhou et al. 2022).
Returning to the two points with which we began this section, and taking into account the cited disagreements in the literature, it seems that:
- Given how complex cognition is, viewing “cognitive impairment” as a monolithic phenomenon is likely a misleading over-simplification.
- Given how complex the maintenance of equilibrium is, it is plausible that different aspects of equilibrium could be differentially affected by different cognitive deficits.
We would therefore agree with the position that, “The method used to define cognitive impairment and the type of fall outcome are both important when quantifying [fall] risk” (Muir et al. 2012). In other words, defining the problem (what kind of cognitive impairment?) and the outcome measure (what aspect of equilibrium?) is crucial in designing a study and interpreting its results. Since different studies do this in different ways, it is unsurprising that there is little consensus in the literature.
Pathophysiological mechanism of disease
There are several possible relationships between cognitive impairment and disequilibrium to consider.
- Cognitive impairment and disequilibrium are associated, but merely co-occur (i.e., are co-incident), without any causal relationship.
- Cognitive impairment and disequilibrium can both result from some common underlying factor (such as age-related attrition of function).
- Cognitive impairment causes disequilibrium.
- Disequilibrium causes cognitive impairment. We discuss this possibility elsewhere.
- Some combination of the above.
The picture is further complicated by the fact that the prevalence of cognitive impairment (from any cause) increases with advancing age, but advancing age brings a host of other medical problems that can adversely affect a person’s balance, a partial list of which includes:
- Sensory impairments
- Visual impairment. Visual impairment is a known risk factor for falls (Lord 2006; Lord and Dayhew 2001), including common age-related conditions such as cataracts (McCarty et al. 2002) and macular degeneration (Alexander et al. 2014).
- Hearing impairment. The relationship between hearing loss and disequilibrium is controversial, and we discuss this elsewhere.
- Diminished somatosensory input.
- Motor impairments
- Orthopedic problems, which can adversely affect joint mechanics (through pain, limitation of flexibility and range of motion) required for maintaining an upright posture and locomotion.
- Deconditioning.
- Reduced muscle mass.
- Other
- Polypharmacy.
- Reduced endurance.
- Cardiovascular problems, such as orthostatic intolerance.
With all the caveats mentioned above, what are some of the mechanisms by which cognitive impairment might contribute to disequilibrium?
- Impaired visuo-spatial abilities (Lee et al. 2020).
- Impaired attention (Ambrose et al. 2013)
- Impaired executive function (Ambrose et al. 2013; Muir et al. 2012; Taylor et al. 2018).
- Impaired judgment (Taylor et al. 2018).
- Reduced response times (Taylor et al. 2018).
- Reduced ability to navigate obstacles (Pieruccini-Faria et al. 2019).
Clinical presentation
Since there are numerous causes of cognitive impairment, there is no uniform manner in which such patients present to an otoneurology or neuro-otology clinic. A common history is one of insidiously progressive disequilibrium beginning within months or a few years of the similarly insidious onset of cognitive impairment. The clinician should be alert to the possibility that although symptoms (cognitive or vestibular) may be reported to have developed “acutely,” often the circumstance is one in which the patient (or their family members) have abruptly recognized symptoms that had been gradually progressing over months to years.
Physical examination
There are no pathognomonic findings on physical examination from which a clinician could conclude that cognitive impairment is the cause of disequilibrium.
Ocular motor examination
There are no pathognomonic findings on ocular motor examination from which a clinician could conclude that cognitive impairment is the cause of disequilibrium.
That being said, some neurodegenerative disorders known to cause cognitive impairment and disequilibrium may have reasonably sensitive and specific findings on ocular motor examination, such progressive supranuclear palsy (PSP), which usually exhibits slowing of vertical saccades.
Testing
There are no sensitive or specific tests (vestibular or otherwise) or imaging from whose results a clinician could conclude that cognitive impairment is the cause of disequilibrium. The main role of such tests and imaging would be to identify alternative diagnoses.
Differential diagnosis
As of this writing it is probably fair to say that the relationship between cognitive function and equilibrium is still being explored, and the literature has not yet reached a clear consensus.
Practically, when an elderly patient with some type of cognitive impairment presents to an otoneurologist or neuro-otologist with a chief complaint of disequilibrium, it is medically reasonable to screen for more common causes of disequilibrium (benign paroxysmal positional vertigo, vestibular weakness, etc.) before concluding that the disequilibrium is the result of cognitive impairment alone.
Treatment and prognosis
If an adequate otovestibular workup reveals no other clear cause for disequilibrium, then it is medically reasonable to use cognitive impairment (of whatever type) as a provisional explanation for the disequilibrium.
If the source of cognitive impairment is treatable (e.g., hypothyroidism, vitamin B12 deficiency, normal pressure hydrocephalus, neurosyphilis) (Bello and Schultz 2011; Takada et al. 2003; Tripathi and Vibha 2009), then the patient’s cognitive neurologist will undertake treatment, even if the likelihood of such intervention bringing about a corresponding improvement in the symptom of disequilibrium is unknown.
In the meantime, it is also medically reasonable to refer the patient for vestibular rehabilitation therapy and for a home safety assessment (usually by an occupational therapist), with the goal of reducing the risks of falls and injuries.
References
Alexander MS, Lajoie K, Neima DR, Strath RA, Robinovitch SN, Marigold DS (2014) Effects of age-related macular degeneration and ambient light on curb negotiation. Optom Vis Sci 91: 975-89. doi: 10.1097/OPX.0000000000000286
Allali G, Annweiler C, Blumen HM, Callisaya ML, De Cock AM, Kressig RW, Srikanth V, Steinmetz JP, Verghese J, Beauchet O (2016) Gait phenotype from mild cognitive impairment to moderate dementia: results from the GOOD initiative. Eur J Neurol 23: 527-41. doi: 10.1111/ene.12882
Allali G, Launay CP, Blumen HM, Callisaya ML, De Cock AM, Kressig RW, Srikanth V, Steinmetz JP, Verghese J, Beauchet O, Biomathics C (2017) Falls, Cognitive Impairment, and Gait Performance: Results From the GOOD Initiative. J Am Med Dir Assoc 18: 335-340. doi: 10.1016/j.jamda.2016.10.008
Ambrose AF, Paul G, Hausdorff JM (2013) Risk factors for falls among older adults: a review of the literature. Maturitas 75: 51-61. doi: 10.1016/j.maturitas.2013.02.009
Bahureksa L, Najafi B, Saleh A, Sabbagh M, Coon D, Mohler MJ, Schwenk M (2017) The Impact of Mild Cognitive Impairment on Gait and Balance: A Systematic Review and Meta-Analysis of Studies Using Instrumented Assessment. Gerontology 63: 67-83. doi: 10.1159/000445831
Bello VME, Schultz RR (2011) Prevalence of treatable and reversible dementias: A study in a dementia outpatient clinic. Dement Neuropsychol 5: 44-47. doi: 10.1590/S1980-57642011DN05010008
Bridenbaugh SA, Kressig RW (2014) Quantitative gait disturbances in older adults with cognitive impairments. Curr Pharm Des 20: 3165-72. doi: 10.2174/13816128113196660688
Chantanachai T, Sturnieks DL, Lord SR, Payne N, Webster L, Taylor ME (2021) Risk factors for falls in older people with cognitive impairment living in the community: Systematic review and meta-analysis. Ageing Res Rev 71: 101452. doi: 10.1016/j.arr.2021.101452
Delbaere K, Kochan NA, Close JC, Menant JC, Sturnieks DL, Brodaty H, Sachdev PS, Lord SR (2012) Mild cognitive impairment as a predictor of falls in community-dwelling older people. Am J Geriatr Psychiatry 20: 845-53. doi: 10.1097/JGP.0b013e31824afbc4
Doi T, Shimada H, Park H, Makizako H, Tsutsumimoto K, Uemura K, Nakakubo S, Hotta R, Suzuki T (2015) Cognitive function and falling among older adults with mild cognitive impairment and slow gait. Geriatr Gerontol Int 15: 1073-8. doi: 10.1111/ggi.12407
Kang GE, Yang J, Najafi B (2020) Does the Presence of Cognitive Impairment Exacerbate the Risk of Falls in People with Peripheral Neuropathy? An Application of Body-Worn Inertial Sensors to Measure Gait Variability. Sensors (Basel) 20. doi: 10.3390/s20051328
Kuan YC, Huang LK, Wang YH, Hu CJ, Tseng IJ, Chen HC, Lin LF (2021) Balance and gait performance in older adults with early-stage cognitive impairment. Eur J Phys Rehabil Med 57: 560-567. doi: 10.23736/S1973-9087.20.06550-8
Lee HW, Lim YH, Kim SH (2020) Dizziness in patients with cognitive impairment. J Vestib Res 30: 17-23. doi: 10.3233/VES-190686
Leroy V, Martinet V, Nunkessore O, Dentel C, Durand H, Mockler D, Puisieux F, Fougere B, Chen Y (2023) The Nebulous Association between Cognitive Impairment and Falls in Older Adults: A Systematic Review of the Literature. Int J Environ Res Public Health 20. doi: 10.3390/ijerph20032628
Liang H, Yue Z, Liu Y, Yan Z, Wang B, Xiang N, Liu E (2023) Association between mild cognitive impairment and falls among Chinese older adults: the mediating roles of balance capacity and depressive symptoms. Inj Prev 29: 173-179. doi: 10.1136/ip-2022-044743
Lord SR (2006) Visual risk factors for falls in older people. Age Ageing 35 Suppl 2: ii42-ii45. doi: 10.1093/ageing/afl085
Lord SR, Dayhew J (2001) Visual risk factors for falls in older people. J Am Geriatr Soc 49: 508-15.
McCarty CA, Fu CL, Taylor HR (2002) Predictors of falls in the Melbourne visual impairment project. Aust N Z J Public Health 26: 116-9. doi: 10.1111/j.1467-842x.2002.tb00902.x
Muir SW, Gopaul K, Montero Odasso MM (2012) The role of cognitive impairment in fall risk among older adults: a systematic review and meta-analysis. Age Ageing 41: 299-308. doi: 10.1093/ageing/afs012
Pieruccini-Faria F, Sarquis-Adamson Y, Montero-Odasso M (2019) Mild Cognitive Impairment Affects Obstacle Negotiation in Older Adults: Results from “Gait and Brain Study”. Gerontology 65: 164-173. doi: 10.1159/000492931
Seijo-Martinez M, Cancela JM, Ayan C, Varela S, Vila H (2016) Influence of cognitive impairment on fall risk among elderly nursing home residents. Int Psychogeriatr 28: 1975-1987. doi: 10.1017/S1041610216001113
Takada LT, Caramelli P, Radanovic M, Anghinah R, Hartmann AP, Guariglia CC, Bahia VS, Nitrini R (2003) Prevalence of potentially reversible dementias in a dementia outpatient clinic of a tertiary university-affiliated hospital in Brazil. Arq Neuropsiquiatr 61: 925-9. doi: 10.1590/s0004-282×2003000600007
Taylor ME, Butler AA, Lord SR, Delbaere K, Kurrle SE, Mikolaizak AS, Close JCT (2018) Inaccurate judgement of reach is associated with slow reaction time, poor balance, impaired executive function and predicts prospective falls in older people with cognitive impairment. Exp Gerontol 114: 50-56. doi: 10.1016/j.exger.2018.10.020
Tripathi M, Vibha D (2009) Reversible dementias. Indian J Psychiatry 51 Suppl 1: S52-5.
Tyrovolas S, Koyanagi A, Lara E, Santini ZI, Haro JM (2016) Mild cognitive impairment is associated with falls among older adults: Findings from the Irish Longitudinal Study on Ageing (TILDA). Exp Gerontol 75: 42-7. doi: 10.1016/j.exger.2015.12.008
Zhang XM, Yuan L, Guo N, Bo HX, Jiao J, Wu XJ, Xu T (2021) Cognitive Frailty and Falls in a National Cohort of Older Chinese Inpatients. J Nutr Health Aging 25: 993-998. doi: 10.1007/s12603-021-1670-y
Zhou R, Li J, Chen M (2022) The Association Between Cognitive Impairment and Subsequent Falls Among Older Adults: Evidence From the China Health and Retirement Longitudinal Study. Front Public Health 10: 900315. doi: 10.3389/fpubh.2022.900315
