Nocturnal polyuria drives nocturia in Parkinson’s disease

<h3>Background</h3> Nocturia is the most common lower urinary tract symptom (LUTS) in Parkinson’s disease (PD) and impacts sleep and subsequent daytime function. Historically nocturia has been attributed to overactive bladder, however we explored the contribution of nocturnal polyuria (NP), the over- production of urine at night. <h3>Methods</h3> This was a sub-study nested within a trial for LUTS in PD. All participants performed 72-hour bladder diaries. Nocturnal polyuria index (NPi) and nocturnal urine production rate (NUP) were calculated from diaries and key associations explored. <h3>Results</h3> 62.6% of participants had NP based on the NPi33 threshold (producing &gt;33% urine at night) and 39.1% based on NUP90 (night-time production rate &gt;90ml/hr). Increasing NPi and NUP were strongly significantly associated with greater nocturia (OR 1.7 per 5% NPi unit; 1.5–2.0; P&lt;0.001, OR per 10ml NUP 1.3; 1.2–1.3; P&lt;0.001 respectively). A significant association was observed between NPi and orthostatic hypotension (OR 1.2 per 5% NPi unit increase; 1.0–1.4; P=0.026) and reported cardiovascular symptoms (coefficient 0.07; 0.03–0.11; P=0.002). A marked association was seen with severe NP and orthostatic hypotension (OR 4.9; 1.56- 15.57; P=0.006). <h3>Conclusion</h3> NP is prevalent and closely associated with increasing nocturia. NP is linked to autonomic dysfunction, particularly blood pressure lability which may be causative.