Hypothesis / aims of study
There is an unexplained association between falls and lower urinary tract symptoms (LUTS) in older adults. The nature and causes of this association are unknown, but it has been suggested that cognitive factors play a role [1]. A moderate desire to void has been shown to influence impulsive decision-making [2], and overactive bladder (OAB) may be as much a disorder of the brain as it is of the bladder. Previous work by our group has demonstrated an increase in reaction time in young, healthy volunteers of around 15% when experiencing a strong desire to void [3], suggesting that the strong desire to void has an effect on cognitive performance in young, continent adults, and may be acting as a source of diverted attention.
We hypothesised that this effect would also be present in older adults, and that the strong desire to void acts as a source of diverted attention, leading to deterioration in a simultaneously-performed cognitive task. This study use a timed cognitive task performed undistracted, while being distracted, and when experiencing a strong desire to void (SDV) in older adults who do not have lower urinary tract symptoms in order to test this hypothesis.
Study design, materials and methods
Older adults, aged 65 and over, were recruited by advertising in the local press and newsletters in seniors’ cenres. Study participants had no significant LUTS, defined as a Bladder Self Assessment Questionnaire (B-SAQ) score of 4 or less, and were cognitively intact, defined as a Montreal Cognitive Assessment Score (MoCA) of 26 or more. Exclusion criteria were neurological disease that may affect cognitive function, such as Parkinson’s disease, sensory impairment that would affect data collection, and use of a urinary catheter or dialysis. Following unformed consent, participants completed two validated cognitive tests, the Trail Making B test and a computer based test of simple reaction time (SRT). The tests were completed under three conditions; undistracted, when being distracted by a simultaneous cognitive task, the n-back test, and when experiencing SDV.
In the Trail Making B test, a validated test of executive function, participants are asked to link a series of 25 circles on a piece of paper, each containing either a number (1-13) or a letter (A-L), alternating letter to number and increasing in sequence. The test was performed twice and the average time taken to complete the task was recorded. For the test of reaction time, participants pressed the space bar on a computer keyboard as quickly as possible after a visual signal changed from red to green. The average of 5 reactions was recorded.
Distraction was induced by the simultaneous performance of an auditory n-back test, in which a series of letters is read to the participant, and if the letter is the same as one two prior in the sequence they indicated this verbally. SDV was induced by drinking non-alcoholic and uncaffeinated drinks ad libitum until they experienced an urge to pass urine that they were unable to defer any longer. This was explained to the participants as being the state at which they would leave a good movie to go to the toilet were they in a cinema.
To reduce learning effects participants were given a practice run of each of the cognitive tests, and the states under which participants performed the tests (undistracted, distracted, and SDV) were performed at random.
The time taken to complete each test under each of the three conditions was compared using student’s T test for pairwise comparisons from undistracted to distracted and undistracted to SDV. Using the results from similar work in young adults for SRT in the undistracted and SDV state [3] we aimed to recruit 23 participants.
Results
21 people were recruited, 8 male and 13 female. The mean age was 74.4 years (SD 5.8). All participants successfully completed data collection and there were no adverse incidents.
When undistracted, the time taken to complete the TMT-B was 76.9 (SD 25.9) seconds. This increased significantly to 140.1 (SD 56.5) seconds with distraction (p<0.001) but was unnafected by the strong desire to void (p=0.523). The mean reaction time was 451ms when undistracted (SD 110). This increased significantly with both distraction (885ms, SD 115) and the strong desire to void (515ms, SD 115), p<0.001 for both.
The results are summarised in Table 1.
Interpretation of results
When compared to the undistracted state, both SDV and the n-back test induced a significant increase in simple reaction time in older adults without lower urinary tract symptoms. Experiencing a SDV increased the reaction time by 64ms (12%), which was a similar effect to that observed in younger adults without LUTS [3]. In context, this increase is equivalent to that seen following 40 hours of sleep deprivation and twice that seen at the legal driving limit for alcohol. A validated source of distraction induced a similar but larger effect, suggesting that the strong desire to void may be acting as a source of diverted attention in continent, older volunteers.
Concluding message
This is the first study to demonstrate a similar cognitive impact of distraction and a strong desire to void in continent, older adults. These results suggest that cognitive performance is impaired by a strong desire to void, even in those without lower urinary tract symptoms. This has implications for the performance of skilled tasks, which rely on rapid reaction, such as driving, when experiencing the urge to pass urine. Diverted attention may be part of the link between falls and LUTS in older adults. These results support the concept that the urge to void acts as a source of diverted attention. Future research should replicate these tests in older adults with LUTS.