Abstract
Background:
Patients with dementia commonly suffer from symptoms of overactive bladder (OAB); however, limited research exists on the clinical impact of coexisting OAB among patients with dementia. As such, the objective of this study was to examine the impact of OAB on clinical outcomes, health-care resource use, and associated costs among patients with dementia.
Methods:
We conducted a retrospective cohort analysis of patients with dementia using 3861 matched pairs of patients with and without OAB. Analyses were based on administrative claims data from January 1, 2007, to September 30, 2015, and compared clinical outcomes, health services use, and associated costs.
Results:
Patients with dementia and OAB were more likely than those without OAB to have least one fall (incidence rate ratio [IRR]: 1.43, 95% confidence interval [CI], 1.22-1.68, P < .001), fracture (IRR: 1.23, 95% CI, 1.05-1.44, P = .008), combined fall/fracture (IRR: 1.25, 95% CI, 1.11-1.42, P < .001), or urinary tract infection (IRR: 2.75, 95% CI, 2.55-2.96, P < .001). Patients with dementia and OAB demonstrated greater utilization of all-cause encounter types compared to similar patients without coexisting OAB (P < .01). All-cause and dementia-related total health-care costs were approximately 23% (95% CI, 0.19-0.28, P < .001) and 13% (95% CI, 0.05-0.20, P = .001), respectively, greater than similar patients without coexisting OAB.
Conclusion:
Coexisting OAB was associated with impacts on clinical outcomes, health-care resource utilization, and costs in patients with dementia.
Keywords: overactive bladder, dementia, health-care resource utilization, fractures, falls, costs
Introduction
Dementia often impacts older individuals and is growing in prevalence as the US population ages. A 2010 study estimated 14.7% of individuals older than 70 years in the United States had some form of dementia. 1 The total monetary costs of this disease were estimated between $157 and $215 billion, with 75% to 84% of costs attributable to institutional and home-based long-term formal and informal care. 1 While the societal and economic costs are substantial, the associated disability, negative impacts on quality of life, and mortality carry as great an impact on the individual patient.
Patients with dementia commonly suffer from other comorbidities that may be overlooked or underdiagnosed, also potentially contributing to additional morbidity and mortality in patients with dementia. 2 Urinary incontinence, a symptom of overactive bladder (OAB), is one such comorbidity diagnosed up to 3 times more in community-dwelling patients with dementia. 3 The OAB syndrome has been defined by the International Continence Society as urinary urgency, generally with frequency and nocturia with or without urgency urinary incontinence. 4 The occurrence of OAB rises with age and is diagnosed in approximately 30% to 40% of those older than 75 years. 5 The OAB has independently been associated with substantial impact on humanistic, clinical, and economic outcomes. 6 -8
Specifically, falls and fall-related injuries (eg fractures) are a concern in patients with OAB, as well as in patients with dementia; these events can lead to increased mortality, in addition to increased health-care utilization and costs. 8 -13 Patients with dementia have been cited to be at significantly increased risk of sustaining a fracture, particularly a hip fracture, than a patient without dementia or a member of the general population. 2,14 -16 With regard to OAB, both dementia and OAB are cited predictors in the risk of falls and fall-related injuries. 7,9,12,15 For example, Brown et al 7 reported that women with weekly urge incontinence had a 26% greater risk of sustaining a fall and a 34% increased risk of fracture. More frequent incontinence was also associated with an increased risk of falls or fractures, and women with daily urge incontinence had increased risks of 35% and 45% of sustaining falls and fractures, respectively.
Outcomes related to OAB and dementia have been explored independently; however, little is known on the specific impact of coexisting OAB among patients with dementia. The purpose of this study was to examine the impact of OAB on clinical outcomes, such as falls and fractures, health-care resource use, and associated costs among patients with dementia.
Methods
Data Source
The Humana Research Database was the data source for this study. The administrative claims database includes enrollment files, medical claims, and outpatient pharmacy claims data from Humana, a US-based company that provides Medicare Advantage, stand-alone Medicare Prescription Drug Plan, and commercial plan offerings. This study was conducted in the Medicare Advantage population. The research protocol was reviewed and approved prior to study initiation by an independent institutional review board.
Study Design
This historical cohort analysis compared health-care resource utilization, costs, and select clinical outcomes for Medicare Advantage Prescription Drug plan patients with dementia with and without OAB. The study included a cohort of patients with prevalent dementia and newly diagnosed coexisting OAB, and a matched cohort of patients with prevalent dementia without coexisting OAB.
Individuals ≥65 years of age, diagnosed with dementia from January 1, 2010, through September 30, 2014, were identified based on the presence of a dementia diagnosis code on one inpatient claim, 2 outpatient claims on separate days, or a prescription claim for a dementia medication in combination with an outpatient claim for dementia. Dementia International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes and medications are listed in Supplementary material, which are based upon the Centers for Medicare & Medicaid Services Chronic Conditions Data Warehouse (CCW) definitions. 17
Patients with OAB were identified based on the presence of at least 1 inpatient or outpatient claim for an OAB symptom (ICD-9-CM: 596.5, 596.51, 788.3, 788.33, 788.41, 788.43, 788.63, 788.91) or a prescription claim for a medication to treat OAB (darifenacin, fesoterodine, oxybutynin, solifenacin, tolterodine, trospium, mirabegron). Date of first observed diagnosis of OAB (or date of first prescription for OAB medication) served as the index event. Only patients where the diagnosis of OAB followed the diagnosis of dementia were included. This ensured an OAB incident-based cohort with known OAB start dates where their health resource utilization and costs were captured for the duration of the study. Patients with dementia and OAB were matched to those with dementia without a diagnosis or medication treatment indicative of OAB at any time during health plan enrollment. For these patients, a pseudo-index date was assigned to approximate the distribution of the index date in the OAB group. 18
Dementia diagnoses were determined using all available preindex (prediagnosis of OAB) medical and pharmacy claims data. A 12-month preindex continuous enrollment period (also referred to as the baseline period) was used to measure baseline patient characteristics, and a 12-month follow-up period was used to evaluate and compare outcomes between the matched cohorts in the primary analyses. The full study period included data from January 1, 2007, through September 30, 2015. Patients were excluded if there were diagnosis or procedure codes indicative of pregnancy, malignant neoplasms (cancer), renal impairment, hepatic insufficiency or organ transplantation during pre or post-index observation period, diagnosis of neurogenic bladder, trauma in the pre- or postindex period, long-term care stay or hospice in the preindex period, or drug/alcohol-induced dementia or dementias related to other medical conditions.
Measures
Clinical outcomes
The number and proportion of patients with at least 1 fall, fracture, combined fall/fracture, urinary tract infections (UTIs), or skin infections/ulcers were measured. The number of cases, the crude incidence rate per 1000 persons, and the incidence rate ratio (IRR) with 95% confidence intervals (CI) were additionally reported. Falls were measured using E codes. Additionally, as a proxy for falls or nonfracture injuries, diagnoses and procedures for dislocations (not due to trauma) were captured. 19 Fractures were identified based on diagnosis and procedure codes. The number and proportion of patients with an indication of at least 1 fall or fracture (fall/fracture) was measured. All fall/fracture claims that occurred within 180 days were considered as part of the same fall/fracture episode. Fall/fracture claims that occurred after 180 days of the last observed date in the initial fall/fracture episode were considered a discrete fall or fracture event. 20,21 The UTIs and skin infections/ulcers were identified in the postindex period based on diagnosis codes. Then the number of patients with an indication of at least 1 UTI or skin infection/ulcer in the postindex period and the median total number of UTIs or skin infections/ulcers were additionally reported. A UTI or skin infection/ulcer was considered a new event if it was more than 30 days after an initial event. All codes used for identification of clinical outcomes are listed in Supplementary material.
Health-care resource utilization
Health-care resource utilization, including physician encounters, outpatient visits, inpatient admissions (acute and nonacute), and emergency department (ED) visits, were measured and reported for all-cause and dementia-related encounters. Claims were considered dementia-related if there was a primary ICD-9 diagnosis in the claim for dementia (Supplementary material) or an indication of a fall/fracture not associated with a coded trauma (eg, car accident) in any claims position. The number and proportion of patients with at least 1 visit by place of service (physician encounter, outpatient visits, inpatient hospital admissions, ED visits) and the total number of health-care resource utilization events by place of service were measured and reported separately. For inpatient admissions, the average total length of stay, in days, was measured. Pharmacy utilization was reported as the total number of unique medications (all-cause) and total number of unique medications indicated for the treatment of dementia (dementia-related).
Health-care costs
Medical costs were calculated for inpatient admissions (acute and nonacute), ED visits, physician encounters, and outpatient visits for all-cause and dementia-related encounters. Dementia-related costs were defined as costs associated with dementia-related health-care resource utilization claims, as defined previously. Pharmacy costs were calculated using outpatient pharmacy claims. Total costs were calculated as the sum of medial and pharmacy costs. Costs were reported in 2010 dollars, using the Bureau of Labor and Statistics Consumer Price Index medical component to adjust all costs to the baseline year of measurement.
Covariates and other measures
The demographic and enrollment characteristics of the patient populations, including age, sex, race/ethnicity, geographic region, and plan benefit type, were measured. Charlson Comorbidity Index score, based on the Quan-enhanced ICD-9 set, and the number of Elixhauser comorbid conditions were measured. 22,23 In addition, the RxRisk-V score, a prescription claims-based comorbidity index, was measured. 24,25
Dementia-related diagnoses were measured: number and percentage of patients with an Alzheimer’s disease (AD) diagnosis, non-AD diagnoses, memory loss, and mild cognitive impairment. Use of medications for dementia and associated neuropsychiatric conditions were assessed: cognitive enhancers (acetylcholinesterase inhibitors [AChEIs], N-methyl d-aspartate receptor antagonists), antidepressants, antipsychotics, and anticonvulsants/mood stabilizers. Patients were considered dementia treated if they received at least 1 prescription for a cognitive enhancer (ie, AChEIs or memantine). Cumulative days’ supply for any cognitive enhancer, the total number of unique dementia treatments received and the number of days from the first observed dementia diagnosis to the index date were reported.
Baseline risk factors for falls/fractures were measured. Use of medications that may increase risk of falls/fractures (eg, benzodiazepines, barbiturates, sedative hypnotics, antidepressants, antipsychotics, anticonvulsants, opioids, antihypertensives, oral or inhaled glucocorticoids, and proton pump inhibitors), and medical conditions associated with falls/fractures (Parkinson's disease, dementia type, hypertension, diabetes, and rheumatoid arthritis), smoking, obesity, and alcohol abuse/dependence were assessed based on claims data. Additionally, the anticholinergic burden was measured using the Anticholinergic Cognitive Burden scale. 26
Statistical Analysis
Propensity score matching was used to balance the comparison groups with respect to all measured baseline demographic, utilization, and clinical characteristics, as described above. This was an efficient approach to matching the patients with dementia and OAB to patients with dementia without OAB on multiple characteristics without the level of attrition that may result from an exact matching process on a large set of variables. The propensity score was estimated using a logistic regression model where OAB status was the outcome. The model was developed using an iterative approach of model fitting and balance checking. 27 The final model included 59 a priori specified potential confounders and 1 empirically identified variable. The cohorts were propensity score matched in a 1:1 ratio using the nearest neighbor match methodology without a caliper and replacement. 28 All patients with dementia and OAB were able to be matched, given the specified matching method and criteria, to an eligible patient with dementia without OAB based on propensity scores. Standardized differences for all variables were evaluated postmatch, all of which were <0.10 indicating good balance across the matched cohorts.
Descriptive statistics, including counts, proportions, means, and medians with appropriate measures of variance (standard deviation and interquartile range), were used to report all-cause and dementia-related health-care resource utilization and costs during the follow-up period. Rates of falls and fractures are reported as crude incidence rate per 1000 persons and the incidence rate ratio with 95% CI. Bivariate analyses were used to compare health-care resource utilization, clinical outcomes, and costs. Wilcoxon rank-sum test was used for non-normally distributed continuous variables, t test for normally distributed continuous variables, χ2 for categorical variables, and 2-sided exact tests for incidence rates. The incremental impact of OAB on all-cause and dementia-related total health-care costs was determined independently using a generalized linear model with a gamma distribution and log-link where all-cause or dementia-related total health-care costs in the follow up period was the dependent variable and “OAB status” was the independent variable. The regression coefficient (B) associated with “OAB status” provides the incremental impact of having OAB on the all-cause or dementia-related total health-care costs.
All data analyses were conducted using SAS Enterprise Guide version 7.1 (SAS Institute, Cary, North Carolina) and Stata version 12.0 (StataCorp, College Station, Texas). The a priori α for all inferential analyses was .05, and all statistical tests were 2 tailed.
Results
After the inclusion and exclusion criteria were applied, 3861 patients with dementia and OAB and 20 216 patients with dementia and no OAB were identified, as shown in Figure 1. All patients with dementia and OAB were successfully matched to an individual with dementia but not evidence of OAB. Select baseline characteristics of the postmatch cohorts are provided in Table 1.
Figure 1.
Attrition diagram.
Table 1.
Post-match Baseline Characteristics.a
| Dementia and OAB, n = 3861 | Dementia No OAB, n = 3861 | P Valueb | SDiff | |
|---|---|---|---|---|
| Demographic/socioeconomic | ||||
| Age, years, mean (SD)c | 78.1 (6.2) | 78.3 (6.4) | .350 | −0.021 |
| Sex, female, n (%)c | 2507 (64.9) | 2496 (64.6) | .793 | 0.006 |
| Race, n (%)c | ||||
| White | 3113 (80.6) | 3119 (80.8) | .863 | −0.004 |
| Black | 402 (10.4) | 395 (10.2) | .794 | 0.006 |
| Hispanic | 115 (3.0) | 109 (2.8) | .684 | 0.009 |
| Other races | 231 (6.0) | 238 (6.2) | .739 | −0.008 |
| LIS status, n (%)c | 588 (15.2) | 569 (14.7) | .545 | 0.014 |
| DE status, n (%)c | 388 (10.0) | 365 (9.5) | .378 | 0.02 |
| Clinical characteristics, mean (SD) | ||||
| Baseline Quan-Charlson score | 1.1 (1.3) | 1.1 (1.3) | .479 | 0.016 |
| Baseline Elixhauser countc | 2.3 (1.9) | 2.3 (1.9) | .508 | 0.015 |
| RxRisk-V score | 5.5 (3.1) | 5.6 (3.1) | .414 | −0.019 |
| Other conditions and variables | ||||
| Baseline fall/fracture, n (%)c | 482 (12.5) | 464 (12.0) | .532 | 0.014 |
| Medications associated with risk of fall/fracture, n (%) | 3202 (82.9) | 3192 (82.7) | .763 | 0.007 |
| Conditions associated with risk of fall/fracture, n (%) | 2897 (75.0) | 2831 (73.3) | .086 | 0.039 |
| Anticholinergic Cognitive Burden (ACB) score, mean (SD)c | 2.1 (2.5) | 2.1 (2.5) | .969 | 0.001 |
| Dementia diagnoses and treatments, n (%) | ||||
| Alzheimer’s dementia (AD)c | 1331 (34.5) | 1344 (34.8) | .756 | −0.007 |
| Non-ADc | 2676 (69.3) | 2652 (68.7) | .555 | 0.013 |
| Cognitive enhancer (AChEI)c | 1886 (48.8) | 1900 (49.2) | .750 | −0.007 |
| Cognitive enhancer (memantine)c | 878 (22.7) | 895 (23.2) | .646 | −0.011 |
| All-cause health-care resource utilization | ||||
| Inpatient admission, n (%) | 702 (18.2) | 698 (18.1) | .906 | 0.003 |
| ED visit, n (%) | 1533 (39.7) | 1492 (38.6) | .339 | 0.022 |
| Outpatient visits, mean (SD)c | 14.9 (11.7) | 14.4 (12.4) | .001 | 0.078 |
| Physician encounters, mean (SD)c | 8.7 (6.3) | 8.6 (6.9) | .012 | 0.058 |
| Total number of unique medications, mean (SD)c | 9.7 (6.1) | 9.5 (5.9) | .204 | 0.029 |
| All-cause total health-care costs, median (IQR)c | $5139 (2687, $9849) | $5153 ($2678, $9941) | .748 | 0.007 |
Abbreviations: ACB, anticholinergic cognitive burden; AChEI, acetylcholinesterase inhibitors; AD, Alzheimer disease; DE, dual eligibility; ED, emergency department; LIS, low-income subsidy; OAB, overactive bladder, PPO, preferred provider organization; SD, standard deviation; SDiff, standardized difference.
aThese are only a select number of variables evaluated.
bP value for continuous variables from Wilcoxon test, for categorical variables from χ2.
cVariables included in the propensity score model. However, these are not a comprehensive list of the independent variables included in the final model.
Patients with dementia and coexisting OAB were more likely to experience at least 1 fall (9.6% vs 6.7%, P < .001), fracture (9.4% vs 7.7%, P = .007), combined fall/fracture (14.8% vs 11.9%, P < .001), and UTI (40.5% vs 16.8%, P < .001) than those without coexisting OAB (Table 2). Patients with dementia and OAB were 43% more likely to have a fall (IRR 1.43, 95% CI, 1.22-1.68, P < .001), 23% more likely to have a fracture (IRR 1.23, 95% CI, 1.05-1.44, P = .008), 25% more likely to have a fall or fracture (IRR 1.25, 95% CI, 1.11-1.42, P < .001), and 2.75 times as likely to have a UTI (IRR 2.75, 95% CI, 2.55-2.96, P < .001) than those with dementia without OAB in the 12-month postindex period (Table 3).
Table 2.
Proportion of Patients With Dementia With and Without Overactive Bladder With At Least 1 Occurrence of Each Clinical Outcome.
| Variable | Dementia and OAB, n = 3861 | Dementia No OAB, n = 3861 | P Valuea |
|---|---|---|---|
| Proportion of patients with at least 1 occurrence of each outcome, n (%) | |||
| Falls | 370 (9.6) | 260 (6.7) | <.001 |
| Fractures | 362 (9.4) | 296 (7.7) | .007 |
| Fall or fracture | 572 (14.8) | 460 (11.9) | <.001 |
| UTIs | 1564 (40.5) | 650 (16.8) | <.001 |
| Skin infections/ulcers | 44 (1.1) | 51 (1.3) | .47 |
Abbreviations: CI, confidence interval; OAB, overactive bladder; UTI, urinary tract infection.
aP values are calculated using χ2.
Table 3.
Number of Clinical Outcome Events for Patients With Dementia With and Without Overactive Bladder.
| Dementia and OAB, n = 3861 | Dementia No OAB, n = 3861) | Incidence Rate Ratio | 95% Incidence Rate Ratio CI | P Valuea | |||
|---|---|---|---|---|---|---|---|
| Variable | Number of Events | Incidence Rate Per 1000 Person-Years | Number of Events | Incidence Rate Per 1000 Person-Years | |||
| Fallsb | 380 | 98 | 265 | 69 | 1.43 | (1.22, 1.68) | <.001 |
| Fracturesb | 370 | 96 | 301 | 78 | 1.23 | (1.05, 1.44) | .008 |
| Fall/fractureb | 591 | 153 | 471 | 122 | 1.25 | (1.11, 1.42) | <.001 |
| UTIsc | 2585 | 670 | 941 | 244 | 2.75 | (2.55, 2.96) | <.001 |
| Skin infections/ulcersc | 128 | 33 | 149 | 39 | 0.86 | (0.67, 1.10) | .208 |
Abbreviations: CI, confidence interval; OAB, overactive bladder; UTI, urinary tract infection.
aP values were calculated using 2-sided exact significant tests.
b181 days were used as a washout period before adding additional fall/fracture to the first observed episode.
c30 days were used as a washout period before adding additional UTI/skin infection/ulcer to the first observed episode.
Patients with dementia and OAB had significantly higher all-cause utilization of all encounter types as compared to those with dementia without OAB (Table 4). The exception was no statistically significant difference in total inpatient length of stay (7.22 [17.05] vs 6.03 [6.96], P = .092). Across dementia-related resource use, patients with dementia and OAB had significantly higher utilization across all encounter types as compared to those with dementia without OAB, except for nonacute inpatient stays (0.01 [0.09] vs <0.01 [0.07], P = .115) and home health (7.7% vs 7.3%, P = .412).
Table 4.
Bivariate Analyses of All-cause and Dementia-Related Health-Care Resource Utilization.
| Dementia and OAB, n = 3861 | Dementia No OAB, n = 3861 | P Valuea | |
|---|---|---|---|
| All-cause | |||
| Inpatient utilization, acute (binary), n (%) | 748 (19.4) | 580 (15.0) | <.001 |
| Inpatient admissions (acute), mean (SD) | 0.26 (0.6) | 0.2 (0.5) | <.001 |
| Total length of stay, mean (SD) | 7.22 (17.1) | 6.03 (6.9) | .092 |
| Inpatient admission (nonacute), mean (SD) | 0.05 (0.2) | 0.03 (0.2) | .007 |
| Total length of stay, mean (SD) | 0.92 (5.5) | 0.67 (4.8) | .007 |
| Long-term care, n (%) | 307 (8.0) | 220 (5.7) | <.001 |
| Outpatient visits, mean (SD) | 15.89 (12.8) | 12.35 (12.9) | <.001 |
| Physician encounters, mean (SD) | 9.4 (6.3) | 7.26 (6.2) | <.001 |
| Hospice, n (%) | 0 (0.0) | 0 (0.0) | NA |
| Home health, n (%) | 1776 (46.0) | 1544 (40.0) | <.001 |
| ED utilization (binary), n (%) | 1595 (41.3) | 1320 (34.2) | <.001 |
| ED visits, mean (SD) | 0.95 (1.7) | 0.73 (1.6) | <.001 |
| Total number of unique medications, mean (SD) | 10.78 (6.2) | 9.01 (5.8) | <.001 |
| Dementia-related | |||
| Inpatient utilization, acute (binary), n (%) | 133 (3.4) | 92 (2.4) | .006 |
| Inpatient admissions (acute), mean (SD) | 0.04 (0.2) | 0.03 (0.2) | .005 |
| Total length of stay, mean (SD) | 7.56 (5.9) | 6.34 (5.4) | .024 |
| Inpatient admission (nonacute), mean (SD) | 0.01 (0.1) | <0.01 (0.1) | .115 |
| Total length of stay, mean (SD) | 0.21 (2.9) | 0.11 (1.9) | .115 |
| Long term care, n (%) | 107 (2.8) | 77 (2.0) | .025 |
| Outpatient visits, mean (SD) | 1.06 (3.1) | 0.92 (2.6) | <.001 |
| Physician encounters, mean (SD) | 0.74 (1.3) | 0.64 (1.2) | .004 |
| Hospice, n (%) | 0 (0.0) | 0 (0.0) | NA |
| Home health, n (%) | 299 (7.7) | 280 (7.3) | .412 |
| ED utilization (binary), n (%) | 346 (9.0) | 263 (6.8) | .001 |
| ED visits, mean (SD) | 0.12 (0.5) | 0.09 (0.4) | <.001 |
| Total number of unique medications, mean (SD) | 0.79 (0.8) | 0.75 (0.8) | .021 |
Abbreviations: ED, emergency department; NA, not applicable; OAB, overactive bladder; SD, standard deviation.
aP values are calculated using χ2 or Wilcoxon tests.
Patients with dementia and OAB had all-cause total health-care costs that were 23.0% greater than those with dementia without OAB (B = 0.23, 95% CI, 0.019-0.28, P < .001, Table 5). Patients with dementia and OAB had 13.0% higher dementia-related health-care costs than those with dementia without OAB, which was statistically significant (B = 0.13, 95% CI, 0.05-0.20, P = .001).
Table 5.
Incremental Impact of Overactive Bladder on Costs for Patients With Dementia.a
| Variableb | Coefficient (B) | P Value | Lower 95% CI | Upper 95% CI |
|---|---|---|---|---|
| All-cause total health-care costs | ||||
| OAB status (OAB = 1, no OAB group is reference) | 0.23 | <.001 | 0.19 | 0.28 |
| Total dementia-related health-care costs | ||||
| OAB status (OAB = 1, no OAB group is reference) | 0.13 | .001 | 0.05 | 0.20 |
Abbreviations: CI, confidence interval; GLM, generalized linear model; OAB, overactive bladder.
aAll costs were adjusted to 2010 USD using the medical care component of the Consumer Price Index.
bGLM model (Gamma distribution and log link) was used to examine the impact of OAB condition (0 = No OAB and 1 = Yes OAB) on dementia-related total health-care–related cost (n = 7722).
Discussion
Previous evaluations of patients with OAB and dementia have mainly focused on the impacts of dementia on outcomes relative to those without dementia, or the identification of OAB as a comorbidity significantly associated with dementia 2,3,6 -8 ; in this study, we examined the incremental impact of a coexisting diagnosis of OAB in patients with dementia. Our results indicate that coexisting OAB in patients with dementia was associated with negative clinical outcomes, greater health-care resource utilization, and greater health-care costs as compared to those without coexisting OAB.
In our study, we observed a significantly greater number of patients with coexisting OAB that sustained a fall, fracture, combined fall/fracture, and UTI, compared to patients with dementia without OAB. These findings are consistent with prior research that suggests that OAB is associated with increased risk of fall and/or fractures. Darkow et al 11 found that falls and fractures were observed in 25.3% of patients with OAB as compared to 16.1% of patients without OAB and that patients with OAB were significantly more likely to suffer from cognitive impairment. While the prevalence of falls and fractures was lower in the current study, differences in the study populations, and methods, including differences in the codes used to identify falls and fractures, could explain the differential rates of falls/fractures reported between the 2 studies.
While no prior studies have examined the incremental impact of OAB on health-care resource use in a dementia population, prior evaluations in other populations have also shown increased utilization of health-care resources associated with OAB. Kannan et al 29 reported that patients with OAB or reporting urinary incontinence symptoms were 1.57 times as likely to have an ED visit, 1.56 times as likely to have a hospitalization, and 1.52 times as likely to have a medical provider visit as compared to those without any OAB or urinary incontinence symptoms. These results are generally greater in magnitude than the results of the current study. However, the comparison group in the current study is patients with dementia who may have greater utilization than the general population; thus, a smaller difference between groups was noted. A recent study in patients with OAB with urinary incontinence who also initiated anticholinergic medications also reported that those with OAB had significantly greater rates of hospital admissions, outpatient visits, and prescriptions filled compared to matched controls without OAB. 30 These previous studies demonstrate that these conditions independently result in higher health-care resource utilization when comparing to similar patients without the condition.
Mirroring the health-care resource utilization results, all-cause and dementia-related costs were 23.0% and 13.0%, respectively, higher in patients with dementia with coexisting OAB as compared to those with dementia without OAB. A previous study by Ganz et al noted patients with OAB had $1925 average annual costs; however, their study evaluated direct and indirect costs, of which almost one-third were attributable to indirect costs. 31 Our evaluation reported only direct costs, thus potentially underreporting the full impact of OAB, particularly in patients with complex comorbid conditions such as dementia. Another study estimated that in the first year after OAB diagnosis, total mean medical charges associated with comorbidities for patients with OAB versus those who did not have OAB were $1689 versus $829.34. 11 Although this incremental difference was significant, it is lower than the current study estimates; however, the previous study focused upon only certain comorbidities, whereas our study captured all-cause costs. Further evaluation of the drivers of the cost differences noted in the current study is warranted.
Limitations common to studies using administrative claims data apply to this study. These include lack of availability of certain clinical information (eg, dementia severity) and errors in claims coding. No causal inference can be ascertained from this study, as it was an observational study using retrospective claims data. Because this study uses data from Humana members only, the results have limited generalizability to the general population. However, Humana provides Medicare Advantage, stand-alone prescription drug plan, and commercial health insurance across the United States. OAB is often underdiagnosed; therefore, patients who may have OAB but are not identified by the algorithm may be included in the cohort identified as not having OAB or may have been excluded from the study altogether. Additionally, dementia may not be coded early on when the symptoms of the disease may begin. Some dementias, such as AD, often have long periods of progression; thus, the time from an initial dementia diagnosis to an OAB diagnosis may be extended and symptoms of OAB (eg, urinary incontinence) may develop as part of dementia progression with cognitive decline. However, time from initial dementia diagnosis (based on available data in the claims) to OAB diagnosis was captured and included in the propensity score models, in addition to other potential proxies for dementia severity (eg, medications, health-care utilization). Additionally, only patients who were considered ambulatory (ie, no long-term care stays) were included in an attempt to capture patients in earlier stages of disease. Propensity score models balance on those factors that are known and included in the model but may not balance on other variables. Furthermore, there was a high attrition and switching rate among patients treated with OAB medication; thus, a self-selection bias could have confounded the relationship between OAB treatment and health-care spending.
Coexisting OAB was associated with impacts on clinical outcomes, health-care resource utilization, and cost in patients with dementia. A better understanding of the prevalence and impact of comorbid conditions in patients with dementia is important for supporting individualized patient care.
Supplemental Material
Supplemental Material, Appendix_A for Impact of Coexisting Overactive Bladder in Medicare Patients With Dementia on Clinical and Economic Outcomes by Eleanor O. Caplan, Ibrahim M. Abbass, Brandon T. Suehs, Daniel B. Ng, Katherine Gooch and Derek van Amerongen in American Journal of Alzheimer's Disease & Other Dementias
Acknowledgments
The authors thank Dr Mary Costantino, PhD, for drafting, reviewing, and editing this manuscript. Dr Costantino is an employee of Comprehensive Health Insights (CHI).
Footnotes
The authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Ng is an employee of Astellas. Astellas manufactures mirabegron (Myrbetriq) and solifenacin (VESIcare). Caplan and Suehs are employees of Comprehensive Health Insights, a subsidiary of Humana, which received funding from Astellas for this study. Abbass was an employee of Comprehensive Health Insights and Gooch was an employee of Astellas at the time the study was completed. Suehs owns stock in Humana. Van Amerongen is an employee of Humana.
Funding: The author(s) disclosed receipt of the following financial support for the research,authorship, and/or publication of this article: Caplan and Suehs are employees of Comprehensive Health Insights, a subsidiary of Humana, which received funding from Astellas for this study.
ORCID iD: Eleanor O. Caplan 
https://orcid.org/0000-0002-6467-7606
Supplemental Material: Supplemental material for this article is available online.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Supplemental Material, Appendix_A for Impact of Coexisting Overactive Bladder in Medicare Patients With Dementia on Clinical and Economic Outcomes by Eleanor O. Caplan, Ibrahim M. Abbass, Brandon T. Suehs, Daniel B. Ng, Katherine Gooch and Derek van Amerongen in American Journal of Alzheimer's Disease & Other Dementias