The Relation of Dizziness to Functional Decline Chad Boult, MD,* John Murphy, MD,S Philip Sloane, MD,t Vincent Mor, PhD,€j and Corby Drone, MS 11
Objective: to assess the effect of dizziness on the probability that an older person will die or become functionally disabled within 2 years. Dizziness is a common symptom for which the prognosis is uncertain. This report compares the prognoses for dizzy and not-dizzy older people in order to assist clinicians who diagnose and treat these patients. Design: a prospective study of a representative sample of elderly (70+) non-institutionalized Americans. Elderly subjects (n = 3,798) in the Longitudinal Study of Aging (LSOA) were asked questions about the presence of dizziness, medical conditions, and functional disability in 1984. The cohort was reinterviewed about functional dis-
,
izziness is a symptom that elderly people commonly report in community surveys’-3 and medical office practice^.^-^ Approximately one-fifth of community elders report dizziness that is severe enough to warrant medical attention or to impair daily activities.’ In the medical practices of internists and family physicians, dizziness is the most common complaint of patients aged 75 and older .4,5 Dizziness can refer to any of several different sens a t i o n ~each , ~ of which has many possible causes.6’8It is associated with multiple sensory and functional impairment~,’,~.~,’~ cardiac and cerebral vascular dis-
D
From the * Department of Family Practice and Community Health, University of Minnesota, Minneapolis, Minnesota; t Department of Family Medicine, University of North Carolina, Chapel Hill, North Carolina; and the Departments of Family Medicine, 5 Medical Science, and 11 Economics, Brown University, Providence, Rhode Island. This research was performed at the Center for Gerontology and Health Care Research at Brown University, Providence, Rhode Island. The project was supported in part by a grant from the Alfred P. Sloan Foundation. A version of this paper was presented at the 46th Annual Scientific Meeting of the American Geriatrics Society, Atlanta, Georgia, May, 1990. Address correspondence and requests for reprints to Chad Boult, MD, MPH, UMHC Box 381, 516 Delaware Street SE, Minneapolis, MN 55455.
+
(C)
1991 by the American Geriatrics Society
ability in 1986. Outcome Measure: transition from functional ability to disability after 2 years. Results: Bivariate analyses showed that dizziness predicts functional decline but not mortality. Multivariate models revealed that age, race, sensory impairment, vascular disease, and other morbidity are independent predictors of becoming disabled. Controlling for these potential confounders, dizziness does not predict an increased probability of becoming disabled. Conclusion: Elderly people who are dizzy should be evaluated for the presence of these related conditions. J Am Geriatr SOC39:858-861, 1991
ease,’,’’ and psychiatric problems such as anxiety and depression.’*’2 Clinical management of dizziness by health professionals is hampered by a paucity of information about the natural history of this common com~ 1 a i n t .Whether I~ dizziness leads to impaired functional ability or to falls and their sequelae is unknown. A recent community survey of 1,622 elderly adults in North Carolina found no association between dizziness and the probability of death or institutionalization within 1 year.’ The authors postulated that this negative result could have been caused by unmeasured confounding variables, relatively insensitive measures of functional decline, and/or an insufficient duration of follow-up. In this paper, we report the results of a longer study of the natural history of dizzy older people, one that controls for the possibly confounding effects of vascular disease, sensory impairment, hypertension, arthritis, and diabetes, as well as age, race, and sex. We assessed mortality and loss of functional ability 2 years after a baseline interview to determine if dizziness, irrespective of other confounding variables, increases an older person’s likelihood of dying or becoming functionally disabled.
METHODS Data The National Center for Health Statistics provided the data for this study from the Longitudinal 0002-8614/91 /$3.50
IAGS-SEPTEMBER 1991-VOL. 39, NO. 9
Study of Aging (LSOA), its joint project with the National Institute on Aging. The LSOA is a prospective study of the changes in health and functional ability that accompany aging in the United States. It monitored a representative sample of the nation's noninstitutionalized civilian elderly population (aged 70+) for 6 years (1984-1990). Extensive information about each subject's health, functional abilities, and other characteristicswas obtained during in-home interviews at baseline in 1984. Follow-up information was collected biannually through telephone interviews and continuously through the National Death Index. A detailed description of the LSOA was published in 1987.14 Records of the 1984 and 1986 interviews (released in 1987) provided the data for this study.
DIZZINESS AND FUNCTIONAL DECLINE
859
of such prevalences should also be adjusted to compensate for the selection of geographic clusters of households in the LSOA ~arnple.'~,'~ Neither weighting nor adjusting of standard errors was necessary in this study, however, because we did not estimate any national prevalences. Furthermore, we found no reason to suspect that the relationships between the predictive variables and the outcome variables might be different in the oversampled or clustered subjects when compared to subjects who might have been selected randomly. RESULTS
The prevalence of dizziness among the study's subjects (n = 3,798) was 26.9%. The distributions of the control variables are shown in Table 1. The transitions Variables The presence of dizziness was defined of the study subjects are shown in Figure 1. Almost by an affirmative response to the question, 'Do you 80% of the subjects remained functionally 'able" 2 sometimes have trouble with dizziness?" Functional years after the baseline interviews. Ten percent had ability was defined by the self-reported capacity to died; 10% had become disabled. Extensive analysis of perform, without help, cooking, light cleaning, bathing, the subjects who were excluded from the study because dressing, eating, reaching and using the toilet, and of missing data revealed no evidence of follow-up bias. Bivariate analyses showed that, compared to nontransferring (in and out of bed or chair). Disability was dizzy people, dizzy people are more likely to be disdefined by the inability to perform one or more of these activities without help, or by a subject's presence in a nursing home or on a waiting list to enter a nursing TABLE 1. DISTRIBUTIONS OF CONTROL home. Age in 1984 was coded as 70-74, 75-79, 80VARIABLES 84, or 85+ years. Race was white or non-white. Sex Percent Variable Number was male or female. Vascular disease was defined as having ever had 'a stroke, a myocardial infarction, any Age in 1984 other heart attack, coronary artery disease, angina pec37.3 70-74 1430 75-79 26.9 1021 tons, or hardening of the arteries." Sensory impairment 80-84 23.3 885 was defined as 'a lot of trouble" with vision or hearing 85+ 12.2 462 or 'a little trouble" with both. Other morbidity was Non-white race 11.9 453 defined by subjects' burden of three diseases: arthritis Female sex 2410 63.5 and diabetes in the previous year; hypertension at any Vascular disease 25.6 972 Sensory impairment 23.2 883 time.
Analysis We excluded sequentially from the analyses the data from any subject who either was not functionally 'able" in 1984 (526), was lost to follow-up in 1986 (358), had a proxy respondent in 1984 (284), or provided ambiguous information about his or her functional abilities in 1984 or 1986 (185). The data from the remaining 3,798 subjects were cross-tabulated and then fitted to polychotomous logistic regression m0de1s.l~A polychotomous model accepts data that reflect more than two possible outcomes, eg, remaining 'able," becoming 'disabled," or 'dying." It assumes that the possible outcomes compete with each other and are mutually exclusive. The parameters of the model were estimated by maximizing a likelihood function using an ordinary Newton-Raphson algorithm.'6 The LSOA oversampled racial minorities, very old people, and residents of certain geographic areas. Its raw data, therefore, must be weighted when they are used to estimate national prevalences. Standard errors
Morbidity (arthritis, diabetes, hypertension) 0 1 2 3
1001 1504 1071 141
26.4 39.6 28.2 3.7
1986
1984
Disabled
3016 (79.4%) Able
388
(10.2%)
FIGURE 1. Transitions of LSOA subjects.
860
BOULT ET AL
JAGS-SEPTEMBER 1991-VOL 39, NO. 9
abled (x' = 18.3, P < 0.0001) but not significantly more likely to be dead (x2 = 1.8, P > 0.15) after 2 years. Other significant predictors of becoming disabled are: age, vascular disease, sensory impairment, and morbidity (P < 0.0001). Significant predictors of death include: age, male sex (P < 0.00001), vascular disease (P < 0.001), and sensory impairment (P < 0.01). Dizziness is associated with older age, female sex, vascular disease, sensory impairment, and morbidity (P< 0.0001). Estimation of the parameters of the polychotomous logistic models showed (Table 2) that vascular disease, sensory impairment, and older age predict higher probabilities of death and disability. Morbidity and nonwhite race predict a higher probability of disability; male sex predicts a higher probability of death. Dizziness does not independently predict the probability of either death or disability. In order to assess the sensitivity of these results to our definition of dizziness, we re-estimated the parameters of the models using two alternate definitions. The criterion for dizziness was restricted, first from 'sometimes has trouble with dizziness" to "dizziness prevents normal activities," and then to 'fell because of dizziness." The prevalence of dizziness decreases under these definitions from 26.9% to 8.4% to 3.4%. The effects of the choice of definition for dizziness are shown in Table 3. Dizziness that is severe enough to prevent activities or cause falls tends to predict the loss of functional ability, but the probability that this relationship resulted from chance remains 5% or more, even in this large sample.
TABLE 2. ESTIMATED PARAMETERS OF LOGISTIC MODELS Model of Probability of Becoming Disabled Odds Wald Covariates Ratio 95% CI Statistic Dizziness 1.0 0.8-1.3 0.1 1.9 1.7-2.1 124.9*** Age 1.5 1.0-2.1 4.5' Race Sex 0.8 0.7-1.1 1.7 Vascular disease 1.6 1.2-2.0 12.7** Sensory impairment 2.3 1.8-2.9 41.4*** Morbiditv 1.3 1.1-1.5 10.1* Model of Probability of Dying ~
~~
Dizziness Age Race Sex Vascular disease Sensory impairment Morbidity * P < 0.05. ** P < 0.001. *** P
Objective: to assess the effect of dizziness on the probability that an older person will die or become functionally disabled within 2 years. Dizziness is a common symptom for which the prognosis is uncertain. This report compares the prognoses for dizzy and not-dizzy older people in order to assist clinicians who diagnose and treat these patients. Design: a prospective study of a representative sample of elderly (70+) non-institutionalized Americans. Elderly subjects (n = 3,798) in the Longitudinal Study of Aging (LSOA) were asked questions about the presence of dizziness, medical conditions, and functional disability in 1984. The cohort was reinterviewed about functional dis-
,
izziness is a symptom that elderly people commonly report in community surveys’-3 and medical office practice^.^-^ Approximately one-fifth of community elders report dizziness that is severe enough to warrant medical attention or to impair daily activities.’ In the medical practices of internists and family physicians, dizziness is the most common complaint of patients aged 75 and older .4,5 Dizziness can refer to any of several different sens a t i o n ~each , ~ of which has many possible causes.6’8It is associated with multiple sensory and functional impairment~,’,~.~,’~ cardiac and cerebral vascular dis-
D
From the * Department of Family Practice and Community Health, University of Minnesota, Minneapolis, Minnesota; t Department of Family Medicine, University of North Carolina, Chapel Hill, North Carolina; and the Departments of Family Medicine, 5 Medical Science, and 11 Economics, Brown University, Providence, Rhode Island. This research was performed at the Center for Gerontology and Health Care Research at Brown University, Providence, Rhode Island. The project was supported in part by a grant from the Alfred P. Sloan Foundation. A version of this paper was presented at the 46th Annual Scientific Meeting of the American Geriatrics Society, Atlanta, Georgia, May, 1990. Address correspondence and requests for reprints to Chad Boult, MD, MPH, UMHC Box 381, 516 Delaware Street SE, Minneapolis, MN 55455.
+
(C)
1991 by the American Geriatrics Society
ability in 1986. Outcome Measure: transition from functional ability to disability after 2 years. Results: Bivariate analyses showed that dizziness predicts functional decline but not mortality. Multivariate models revealed that age, race, sensory impairment, vascular disease, and other morbidity are independent predictors of becoming disabled. Controlling for these potential confounders, dizziness does not predict an increased probability of becoming disabled. Conclusion: Elderly people who are dizzy should be evaluated for the presence of these related conditions. J Am Geriatr SOC39:858-861, 1991
ease,’,’’ and psychiatric problems such as anxiety and depression.’*’2 Clinical management of dizziness by health professionals is hampered by a paucity of information about the natural history of this common com~ 1 a i n t .Whether I~ dizziness leads to impaired functional ability or to falls and their sequelae is unknown. A recent community survey of 1,622 elderly adults in North Carolina found no association between dizziness and the probability of death or institutionalization within 1 year.’ The authors postulated that this negative result could have been caused by unmeasured confounding variables, relatively insensitive measures of functional decline, and/or an insufficient duration of follow-up. In this paper, we report the results of a longer study of the natural history of dizzy older people, one that controls for the possibly confounding effects of vascular disease, sensory impairment, hypertension, arthritis, and diabetes, as well as age, race, and sex. We assessed mortality and loss of functional ability 2 years after a baseline interview to determine if dizziness, irrespective of other confounding variables, increases an older person’s likelihood of dying or becoming functionally disabled.
METHODS Data The National Center for Health Statistics provided the data for this study from the Longitudinal 0002-8614/91 /$3.50
IAGS-SEPTEMBER 1991-VOL. 39, NO. 9
Study of Aging (LSOA), its joint project with the National Institute on Aging. The LSOA is a prospective study of the changes in health and functional ability that accompany aging in the United States. It monitored a representative sample of the nation's noninstitutionalized civilian elderly population (aged 70+) for 6 years (1984-1990). Extensive information about each subject's health, functional abilities, and other characteristicswas obtained during in-home interviews at baseline in 1984. Follow-up information was collected biannually through telephone interviews and continuously through the National Death Index. A detailed description of the LSOA was published in 1987.14 Records of the 1984 and 1986 interviews (released in 1987) provided the data for this study.
DIZZINESS AND FUNCTIONAL DECLINE
859
of such prevalences should also be adjusted to compensate for the selection of geographic clusters of households in the LSOA ~arnple.'~,'~ Neither weighting nor adjusting of standard errors was necessary in this study, however, because we did not estimate any national prevalences. Furthermore, we found no reason to suspect that the relationships between the predictive variables and the outcome variables might be different in the oversampled or clustered subjects when compared to subjects who might have been selected randomly. RESULTS
The prevalence of dizziness among the study's subjects (n = 3,798) was 26.9%. The distributions of the control variables are shown in Table 1. The transitions Variables The presence of dizziness was defined of the study subjects are shown in Figure 1. Almost by an affirmative response to the question, 'Do you 80% of the subjects remained functionally 'able" 2 sometimes have trouble with dizziness?" Functional years after the baseline interviews. Ten percent had ability was defined by the self-reported capacity to died; 10% had become disabled. Extensive analysis of perform, without help, cooking, light cleaning, bathing, the subjects who were excluded from the study because dressing, eating, reaching and using the toilet, and of missing data revealed no evidence of follow-up bias. Bivariate analyses showed that, compared to nontransferring (in and out of bed or chair). Disability was dizzy people, dizzy people are more likely to be disdefined by the inability to perform one or more of these activities without help, or by a subject's presence in a nursing home or on a waiting list to enter a nursing TABLE 1. DISTRIBUTIONS OF CONTROL home. Age in 1984 was coded as 70-74, 75-79, 80VARIABLES 84, or 85+ years. Race was white or non-white. Sex Percent Variable Number was male or female. Vascular disease was defined as having ever had 'a stroke, a myocardial infarction, any Age in 1984 other heart attack, coronary artery disease, angina pec37.3 70-74 1430 75-79 26.9 1021 tons, or hardening of the arteries." Sensory impairment 80-84 23.3 885 was defined as 'a lot of trouble" with vision or hearing 85+ 12.2 462 or 'a little trouble" with both. Other morbidity was Non-white race 11.9 453 defined by subjects' burden of three diseases: arthritis Female sex 2410 63.5 and diabetes in the previous year; hypertension at any Vascular disease 25.6 972 Sensory impairment 23.2 883 time.
Analysis We excluded sequentially from the analyses the data from any subject who either was not functionally 'able" in 1984 (526), was lost to follow-up in 1986 (358), had a proxy respondent in 1984 (284), or provided ambiguous information about his or her functional abilities in 1984 or 1986 (185). The data from the remaining 3,798 subjects were cross-tabulated and then fitted to polychotomous logistic regression m0de1s.l~A polychotomous model accepts data that reflect more than two possible outcomes, eg, remaining 'able," becoming 'disabled," or 'dying." It assumes that the possible outcomes compete with each other and are mutually exclusive. The parameters of the model were estimated by maximizing a likelihood function using an ordinary Newton-Raphson algorithm.'6 The LSOA oversampled racial minorities, very old people, and residents of certain geographic areas. Its raw data, therefore, must be weighted when they are used to estimate national prevalences. Standard errors
Morbidity (arthritis, diabetes, hypertension) 0 1 2 3
1001 1504 1071 141
26.4 39.6 28.2 3.7
1986
1984
Disabled
3016 (79.4%) Able
388
(10.2%)
FIGURE 1. Transitions of LSOA subjects.
860
BOULT ET AL
JAGS-SEPTEMBER 1991-VOL 39, NO. 9
abled (x' = 18.3, P < 0.0001) but not significantly more likely to be dead (x2 = 1.8, P > 0.15) after 2 years. Other significant predictors of becoming disabled are: age, vascular disease, sensory impairment, and morbidity (P < 0.0001). Significant predictors of death include: age, male sex (P < 0.00001), vascular disease (P < 0.001), and sensory impairment (P < 0.01). Dizziness is associated with older age, female sex, vascular disease, sensory impairment, and morbidity (P< 0.0001). Estimation of the parameters of the polychotomous logistic models showed (Table 2) that vascular disease, sensory impairment, and older age predict higher probabilities of death and disability. Morbidity and nonwhite race predict a higher probability of disability; male sex predicts a higher probability of death. Dizziness does not independently predict the probability of either death or disability. In order to assess the sensitivity of these results to our definition of dizziness, we re-estimated the parameters of the models using two alternate definitions. The criterion for dizziness was restricted, first from 'sometimes has trouble with dizziness" to "dizziness prevents normal activities," and then to 'fell because of dizziness." The prevalence of dizziness decreases under these definitions from 26.9% to 8.4% to 3.4%. The effects of the choice of definition for dizziness are shown in Table 3. Dizziness that is severe enough to prevent activities or cause falls tends to predict the loss of functional ability, but the probability that this relationship resulted from chance remains 5% or more, even in this large sample.
TABLE 2. ESTIMATED PARAMETERS OF LOGISTIC MODELS Model of Probability of Becoming Disabled Odds Wald Covariates Ratio 95% CI Statistic Dizziness 1.0 0.8-1.3 0.1 1.9 1.7-2.1 124.9*** Age 1.5 1.0-2.1 4.5' Race Sex 0.8 0.7-1.1 1.7 Vascular disease 1.6 1.2-2.0 12.7** Sensory impairment 2.3 1.8-2.9 41.4*** Morbiditv 1.3 1.1-1.5 10.1* Model of Probability of Dying ~
~~
Dizziness Age Race Sex Vascular disease Sensory impairment Morbidity * P < 0.05. ** P < 0.001. *** P
