As we know, no matter male or female patients, nocturia is one bothersome symptom, which severely influence the life quality and may cause depression. Nonetheless, nocturia treatment is complicated due to multiple co-morbidities and etiology. Nocturnal polyuria is one common pathogenesis which could be treated with desmopressin supplement. Hyponatremia is a major concern during the supplement, especially in the elderly patients. In the lack of research regarding the potential risk factors of hyponatremia after desmopressin replacement in the elderly patients with nocturnal polyuria, we herein investigate the risk factors and the incidence of hyponatremia after treatment.

From January 2018 to February 2019 in our institute, those patients who meet the criteria of nocturnal polyuria were recruited in this retrospective study. All patients below the age of 65 were excluded. In addition, each patient  recorded 24 hours voiding diaries for 3 days, including  mean numbers of nocturnal voids,  nocturnal urine volume, and total urine volume. Nocturnal polyuria index was counted and the cut-off value was set at 0.33. Desmopressin 0.1 mg was given orally to all patients before going to bed at night for 3 months. Before treatment and monthly after treatment, mean number of nocturnal voids, questionnaires of adverse events were recorded. Before treatment and both 1month, 2 months and 3 months after treatment, the patients in treatment group had to be checked blood serum sodium.

A total of 29 patients, who greater than 65 years of age, male 26 and female 3, were enrolled in this retrospective study. The average ages of patients were 77 ±8.46 years old. Mean volume of drinking water before and after receiving Desmopressin were 1559.81 ± 547.85 ml and 1321.86 ± 412.7 ml respectively (p value 0.865). Mean volumes of nocturnal voids before and after receiving Desmopressin were 1436.04 ± 353.14 ml and 718.57 ±333.76 respectively (p value 0.003). Mean frequencies of nocturnal voids before and after receiving Desmopressin were 4.84 ± 1.78 and 3.38 ±1.4 respectively (p value 0.007). Mean volumes of first voiding in the morning before and after receiving Desmopressin were 295.13 ±114.75 ml and 270.48 ±104.28 ml respectively (p value 0.944).
3 patients were diagnosed with sleep apnea, but only 1 patient underwent BiPAP therapy with better symptoms relieving of nocturnal polyuria. No serious events occurred and no adverse events of severe intensity were recorded. After 1st month, the change from baseline serum sodium was – 2.955 mmol/L (p value 0.003). Following in 2nd and 3rd month, then change from baseline serum sodium were -2.646 mmol/L (p value 0.008) and-1.312 mmol/L (p value 0.189) respectively. Eight patients (27%) qualified as being sensitive to change in serum sodium, from 118 to 134 mmol/L at first month. They also complained mild nausea (2/8), headlightness (1/8) and abdominal pain (1/8). The symptoms of headlightness was disappeared after 2 days later without changing in the dosage. The model obtained with logistic regression for sensitivity to change in serum sodium has a good predictive power (g power 0.80). .

The risk of hyponatremia was increased with age, using lipid-modifying drugs and prostate hormone therapy. In our study, female patients were with small sample size that lacking significant difference with male patients in relieving of nocturnal polyuria, although higher sensitivity of desmopressin well-known to female due to AVPR2 gene locating on the X chromosome which regulates renal vasopressin type 2 receptor (V2R) and plays a critical role in physiological process associated with AVP-induced antidiuresis

Although the risk of hyponatremia increased with age and medical co-morbidities, the incidence of hyponatremia in the research is low under desmopressin supplement. Low-dose Desmopressin is an effective and well-tolerated treatment for nocturia in elderly patient.