Some epidemiological studies have suggested that the prevalence of lower urinary tract symptoms (LUTs) is higher during winter than summer based on cross-sectional studies, and animal studies have identified cold stress-induced detrusor overactivity. However, the influence of environmental temperature on overactive bladder (OAB) in women has not been reported. Therefore, the present study aimed to identify the impact of outdoor temperature on OAB symptoms in women without pyuria on urinalysis.

Medical records of female patients treated for OAB symptoms from January 2011 to December 2017 were retrospectively reviewed. Patients with pyuria at the first visit, those who did not complete the questionnaire, and those with <3 overactive bladder symptom scores (OABSS) were excluded. Uroflowmetric parameters, 3-day micturition diary, and OABSS were analyzed.

A total of 582 patients with OAB symptoms who visited the hospital were enrolled in this study. Patients were grouped into 1 of the 3 season groups (cold, intermediate, and hot) depending on the average temperature of the month that the patient first visited the urologic department outpatient clinic. The total OABSS was significantly different between the 3 season groups (cold [7.25±3.20] vs. intermediate [6.24±3.40] vs. hot [5.51±3.20], P=0.001). The proportion of patients who had moderate OAB symptoms (6≤OABSS) was higher in the cold season group (56.2%) than in the other season groups (intermediate, 42.1%; hot, 31.8%; P=0.002). Differences in the number of micturitions (12.12±4.56 vs. 10.95±4.39, P=0.021) and number of urgent urinary incontinence episodes (2.06±0.94 vs. 2.48±0.87, P=0.001) between the cold and hot season groups were also significant. However, differences in the nocturia episode, total daytime voided volume, and mean voided volume between season groups were not significant.

OAB was more likely to occur during winter, and the symptoms may also vary with temperature. However, studies about this issue are limited. Previous epidemiologic studies mostly focused on normal populations, and these studies were not able to investigate parameters, such as voiding diary and uroflow. Therefore, consistent results are difficult to obtain. Furthermore, no study on the relationship between temperature and OAB symptoms in female patients has been conducted. In the present study, the total OABSS of the cold season groups was higher than that of other groups. This finding indicates that the symptoms are more severe if the patients visit the hospital on a cold day rather than on a warm day. In addition, patients had a higher frequency and urgency episode in their 3-day micturition diary on cold days. Some physiologic hypotheses state that low temperature is correlated with detrusor overactivity. First, the activity of the sympathetic nervous system associated with transient hypertension partially correlated with the cold stress-induced detrusor overactivity. Second, the transient receptor potential (TRP) channel expression in the skin may be affected in individuals with active bladder symptoms. In a previous animal study, skin temperature was found to be associated with detrusor overactivity  [1].

Different urinary symptoms and uroflowmetric parameters were correlated with seasonal variation. OAB symptom might be worse in cold weather seasons compared with other seasons. Therefore, individuals must maintain a warm environment to prevent OAB.

Ishizuka O, Imamura T, Nishizawa O. Cold Stress and Urinary Frequency. Low Urin Tract Symptoms 2012;4 Suppl 1:67-74.