Abstract
Loss of bladder control (urge incontinence) is common in elderly; the cause is usually unknown. Functional imaging has revealed the brain network controlling responses to bladder filling. Age-related changes in this network might predispose to urge incontinence. We sought such changes in 10 continent, healthy women aged 30-79 years who underwent fMRI while fluid (approximately 20 ml) was repeatedly infused into and withdrawn from the bladder. Data were collected in 4 measurement blocks with progressively increasing bladder volumes and were analyzed by SPM2, using the contrast infuse-withdraw to quantify response to bladder infusion. Effective connectivity was examined by physiophysiological interaction (PhPI; see interpretation in Supplementary Material), with right insula (RI) and dorsal anterior cingulate cortex (dACC) as seed regions. Dependence on age and bladder volume (= block number) was assessed. Bladder infusion evoked expected activations. Activation decreased with age in bilateral insula and dACC. PhPI revealed connectivity with RI and dACC in regions that included bilateral putamen and R pontine micturition center. Interaction (connectivity) tended to increase with age in regions including L insula, L paracentral lobule and PAG. Consistent with a special role in maintaining continence, medial prefrontal cortex (mPFC) showed a trend to deactivation on bladder infusion that became more prominent in old age, and a trend to negative interaction (connectivity) that weakened significantly with age. Thus, with increasing age, weaker signals in the bladder control network as a whole and/or changes in mPFC function or connecting pathways may be responsible for the development of urge incontinence.