Differences of nighttime and daytime bladder capacity in patients with nocturia

This study aimed to investigate the impact of bladder capacity differences on nocturnal polyuria (NP) and nocturia. This study found that severe nocturia is associated with NP and reduced bladder capacity.

Nocturia is the urge to urinate at night. Severe nocturia is when a person gets up more than 3 times a night. Nocturnal polyuria (NP) is urinating at night. It is different from nocturia in that patients urinate more at night than during the day. The total amount of urine made is not changed. 

It is unclear if differences in bladder capacity impacts on nocturia or NP. 

This study included 84 patients. These patients were assessed for NP and reduced bladder capacity. 3-day frequency-volume charts were made for each patient. NP and bladder capacity were calculated for each patient. Reduced bladder capacity was defined as an average bladder capacity less than 200 ml per day.

59.5% of patients had NP and 59.5% had decreased bladder capacity. Higher body mass index and severe nocturia were risk factors for NP. Severe nocturia was associated with reduced bladder capacity. Patients with NP had a different bladder capacity in the day and the night. Every 10 ml increase in bladder capacity during the night reduced the risk of severe nocturia by 12%.

This study found that severe nocturia is associated with NP and reduced bladder capacity.