Hypothesis / aims of study
Overactive bladder (OAB) and cognitive impairment (CI) are both increasingly prevalent with age. Given the known association between anticholinergics and dementia risk, there is a need to optimize other therapies. [1]
Sacral neuromodulation (SNM), a current third-line therapy for OAB, offers an attractive potential non-anticholinergic therapy for older adults. It can be placed under light sedation or local, has been shown to reduce or eliminate anticholinergic use for refractory OAB, and compared to other third-line therapies, intradetrusor onabotulinumtoxinA and percutaneous tibial nerve stimulation, SNM does not require indefinite, ongoing office and procedural visits. [2]
Though American Urologic Association (AUA) and Society for Urodynamics, Female Pelvic Medicine and Urogenital Reconstruction (SUFU) guidelines on OAB cite intact cognitive ability as necessary to maintain OAB therapy, cognitive assessment is not a formal part of perioperative evaluation and there is no data to guide cognitive thresholds for therapy. [3] This study aimed to assess the impact of CI diagnosis on SNM implant rates and device related outcomes in an older OAB population.
Study design, materials and methods
Following institutional review board (IRB 20-1141) approval, a retrospective chart review was performed of patients aged 55 years or older who underwent test-phase SNM (peripheral nerve evaluation (PNE) or stage 1) for OAB or urgency urinary incontinence between January, 2014 and March, 2021 within a large multi-regional health system. The electronic medical record was queried for all SNM test-phase procedures performed during the study period using the appropriate CPT codes (64561, 64581).
Patient demographics and comorbidities, CI diagnoses (dementia or mild cognitive impairment (MCI)), OAB medication and/or botulinum toxin use, and SNM procedures were recorded. Patients were considered to have cognitive impairment if they had any dementia or MCI diagnosis code assigned or had an active dementia medication (donepezil, galantamine, rivastigmine or memantine). SNM procedure outcomes were categorized as implant (Stage 2 or combined Stage1+2), explant, and/or revision of the lead and/or implantable pulse generator (IPG). Manual chart review was performed to confirm all SNM outcomes. Test-phase success was defined as 50% or greater reduction in symptoms documented in the chart. For device revisions and explants, indication was also recorded.
Logistic regression modeling was performed to assess the impact of CI on SNM implantation rate. To do so, a backward-elimination method an α<0.20 criterion was employed. All statistical analyses were performed using R programming language (version 3.6.1).
Results
510 patients underwent SNM test-phase (161 PNE, 349 Stage 1). Mean age was 71.0(8.5) years and 80.6% were female. Overall, 52(10.1%) patients had a CI diagnosis at time of SNM, and 30(5.8%) were diagnosed a median 18.5[9.25, 39.5] months after SNM. Most common CI diagnosis at time of SNM test-phase was MCI (n=17). Patients with CI were older, with more comorbidities and were more likely to undergo PNE (Figure 1). Univariable comparison found no difference in implantation rate based on pre-SNM CI (85.4% vs 76.9%, p=0.16).
Multivariable analysis identified PNE, age, and prior beta-3 agonist use but not CI or dementia as independent negative predictors of implantation (Figure 2). Implanted patients had median urologic follow-up of 17[6.0, 44.0] months. Explant (12.1%), revision (10.4%), and battery replacement (3.4%) rates did not differ according to CI.
Rates of OAB medication cessation with SNM varied by medication across the study sample (Anticholinergic, N=237 (64.6%); B3 agonist, N=137 (77.4%)). However, patients with any CI diagnosis were more likely than those without CI to continue or restart a B3 agonist (37.1% vs 19.0%, p=0.038) after SNM implantation. Treatment with onabotulinumtoxinA after SNM was uncommon (8.3%) and did not differ based on CI.
Interpretation of results
This retrospective study is the first to our knowledge to assess the impact of cognition on SNM outcomes. It identified a high rate of CI in an older OAB cohort pursuing SNM, finding 10% of patients had an active CI diagnosis or dementia medication prescription at the time of their SNM test-phase. Consistent with expectations of SNM, most patients proceeded to permanent implantation, while implant rates did not differ based upon CI. On longer term follow-up, most implanted patients did not continue or restart anticholinergic medications, and device explant and revision rates did not differ based upon CI.
While the AUA/SUFU OAB guidelines note that adequate cognitive ability is necessary for patients to engage with OAB treatment, there is no data to inform a specific cognitive threshold. The cohort of patients in this study present an older refractory OAB population who were offered SNM by experience subspecialist urologists. Thus, patients were presumably deemed appropriate procedural and SNM candidates. Further study is necessary to determine what an appropriate cognitive function threshold may be for successful SNM therapy.