Is nocturia associated with poor nighttime blood pressure reduction?

This study evaluated the relationship between nocturnal polyuria (NP – excessive nighttime urine production) and 24-hour blood pressure (BP) fluctuations in patients with urinary symptoms. The data suggested that patients with NP had a poorer reduction of nighttime BP. 

Nocturia is the need to wake up during the night to urinate. There are several causes of nocturia, including nocturnal polyuria (NP). NP involves excessive nighttime urine production which leads to waking at night to urinate. It can be influenced by excessive fluid intake, hypertension (high blood pressure – BP), and abnormal hormone levels. In patients with nocturia, it is important to find the right cause to establish the best possible treatment.

BP changes throughout 24 hours. It normally decreases during sleep time. It is not clear whether NP is associated with abnormal BP fluctuations throughout 24 hours and if better BP control can improve NP. 

This study involved 90 male patients aged 65 and older with lower urinary tract symptoms (LUTS). These patients were assigned to 2 groups based on the nocturnal polyuria index (based on nighttime urine production in relation to 24-hour urine production. Patients with a higher index had worse NP (group 1 – 44 patients). Group 2 included 46 patients and had a low NP index (non-NP group).

There was no significant difference in BP during the daytime between both groups. However, patients in group 1 had a lower reduction in systolic BP (BP when the heart beats – the higher number in the BP reading) compared to group 2. There was no significant difference in diastolic BP (BP when the heart relaxes between beats – the lower number of the BP reading) during nighttime between groups.

The study concluded that NP was associated with poorer nighttime blood pressure reduction. This may suggest that better BP control during the night might improve NP in these patients. 

This study included only patients in Japan and only males with LUTS. Also, there was no intervention to improve BP in an effort to treat NP. Future interventional studies in a wider population are needed to confirm the findings.