Discussion:
Nocturia is a common health problem in world-wide and its prevalence
vary between 8.9%-82.7% according to inclusion criteria, sex and age
groups.7-9 In US the prevalence of nocturia (≥ 1
voids) was evaluated in different age and sex groups and detected in men
as 56.8%, 70.2% and 82.7% in 20-39 years, 40-59 years and ≥ 60 years
respectively; in women as 68.9%, 74.3% and 84.7% in 20-39 years,
40-59 years and ≥ 60 years respectively.8 The nocturia
prevalence was noted as 28.4%, 17.6% and 8.9% for nocturia episodes
≥ 1, ≥ 2, or ≥ 3 respectively, in Turkey.9 The most
common risk factors of nocturia are age, hypertension, higher body mass
index (BMI), metabolic syndrome, diabetes mellitus and cerebrovascular
and cardiovascular diseases.10,11 Also nocturia was
found to be associated with increased risk of falls, fractures, driving
accidents and mortality.12-14 Nocturia and
nocturia-related morbidities lead serious economic burden on health care
systems of countries.15-17 These nocturia related
risks, morbidities and economic burden reveal the importance of timely
evaluation and effective nocturia management. The main step of nocturia
management is the classification of nocturia according to
pathophysiology. Nocturia can be sub-classified into four
pathophysiological mechanisms: global polyuria (an overall increase of
urine production), nocturnal polyuria (an increase of urine production
only at night), reduced bladder capacity and mixed of
etiologies.3,18,19 One of the first studies about the
classification of nocturia was published by Weiss et al at
1998.20 They classified the nocturia in three groups
as nocturnal polyuria (NP), nocturnal detrusor overactivity (NDO)
(including reduced bladder capacity) and mixed (NP+NDO) and
retrospectively evaluated the data of 200 consecutive patientswith
nocturia.20 They detected that 7% of patients had
nocturnal polyuria, 57% of patients had NDO and 36% of patients had a
mixed etiology.20 They did not add global polyuria in
classification, evaluated it separately and they noted that 23% of
patients had global polyuria. There were some differences in definitions
of nocturia etiologies in this study; they defined nocturnal polyuria as
> 33% of the 24-hour urine production and polyuria as
>2500 cc urine output in 24 hours. The distribution of
nocturia etiologies was different from our study because of definition
criteria and the unsimilar subclassification of etiologies. Choi et al
evaluated the classification of nocturia in male patients with lower
urinary tract symptoms (LUTS).21 A total of 521
patients >18 years old were included in the study and 376
(72.2%) patients had nocturnal polyuria, 520 (99.8%) patients had
reduced bladder capacity, 376 (72.2%) patients has mixed type and 45
(8.6%) patients had global polyuria. Unlike this study the most common
type of nocturia was nocturnal polyuria in our study. The patient
population may have a significant role in different results of the
studies, as they included only male patients with LUTS however we
evaluated both genders and not only patients with LUTS. Epstein et al
compared the nocturia etiology in black and white male patients who
admitted with LUTS between the years 2008 and 2016.22They subclassified nocturia as NP, RBC, mixed (NP+RBC) and other
(neither RBC nor NP) and they reported that 24%, 27%, 30% and 19% of
white patients had NP, RBC, mixed nocturia and other etiologies
respectively; while 26%, 30%, 28% and 16% of black patients had NP,
RBC, mixed nocturia and other etiologies respectively. They noted that
the etiological mechanisms were similar between the groups. The
differences between the percentages of nocturia etiologies form our
study may be also due to the selection of patient criteria and the
differences in the classification of nocturia mechanisms. So we believe
that the standardization of classification of nocturia mechanisms is
important to speak the same language.
Nocturia has negative impacts on quality of life (QoL) of patients and
leads to decrease in productivity at
work.5,15,16,23,24 The effects of nocturia on QoL are
mostly related with the severity of nocturia. Although one or more times
wake up to void at night is defined as nocturia; it was noted that most
of the patients with one nocturia episode had no bother or some of the
older patients considered this as a normal consequence of
aging.5,23,24 Tikkinen et al. evaluated the
association between the nocturia severity and the health related QoL
(HRQoL) of individuals with using generic 15 dimension
instrument.5 Bother of nocturia was evaluated with
four-point scale (none, small, moderate, major) and they noted that
majority of patients with one nocturia episode had no significant bother
however patients with two episodes of nocturia had small bother and
patients with three or more nocturia episodes had moderate or major
bother. Also they reported that ≥2 voids per night were associated with
impaired HRQoL. We classified the nocturia severity as mild, moderate
and severe in our study and reached similar results as they did.
Additionally, we used a nocturia specific quality of life questionnaire,
N-QoL, which was firstly described by Abraham et al25and we found that increased severity of nocturia was associated with
impaired QoL of patients in concordance with previous
studies.5,25 Zhang et al evaluated the prevalence and
risk factors of nocturia and nocturia-related quality of life in Chinese
population with 1198 adults.26 They used also N-QoL
questionnaire and they reported that increasing episodes of nocturia and
decreasing total sleeping hours were independent factors predicting a
significantly lower N-QOL score. Also they noted that two or more
nocturia episodes were associated with worse N-QoL scores as we did.
Fitzgerald et al evaluated the data of 5506 adults at ages 30 to 79 from
Boston Area Community Health (BACH) study; they detected the nocturia
prevalence as 28.4% and the individuals with nocturia had lower
self-rated mental and physical health scores.13However they did not specify the association with nocturia severity and
these scores. Choi et al assessed the mediating role of sleep quality in
the association between the nocturia and HRQoL with 500 patients above
40 years old.27 They reported that ≥2 nocturia
episodes were associated with decreased HRQoL and this association was
mediated by sleep quality. Although some of the studies presented the
threshold ≥2 nocturia episodes for nocturia severity; there has been no
consensus about the severity of nocturia and treatment requirements of
patients regarding to nocturia severity in the existing literature yet.
So, we propose a grading standardization for nocturia severity as mild
(1-2 voids/night), moderate (3-4 voids/night) and severe nocturia
(>4 voids/night) and demonstrate that increase in nocturia
severity was associated with decreased quality of life as well as
different rates of pathophysiological mechanisms.
We also faced that all scores for standardized LUTS questionnaires used
in the present study were higher in more severe nocturia groups.
Abdelmoteleb et al evaluated the association between the ICIQ-bladder
diary and the ICIQ-LUTS.28 They noted that the
agreement level between the ICIQ-bladder diary and the ICIQ-LUTS for
nocturia symptoms was better than that of daytime frequency in both
genders and the agreement level was also higher in at the extreme of
frequencies. Both voiding and storage scores of ICIQ-MLUTS and
ICIQ-FLUTS were also correlated with nocturia severity in our study.
Given the fact that the severity of nocturia was diagnosed with a
bladder diary in the present study, our findings support previous
studies for the concordance of voiding questionnaires and bladder diary.
Several studies reported that the prevalence and severity of nocturia
was increased with aging.9,29 Vaughan et al detected
that the half of the patients with older age had ≥ 2 nocturia episodes
however this rate was only 15-20% in younger patients. Also they noted
that the number of co-morbidities were higher in patients with more
nocturia frequency. Patients with moderate and severe nocturia were
older and had more comorbidities need to treat than mild nocturia in our
study.
Although the treatment of baseline pathology is essential in patients
with nocturia, precautions in lifestyle changes like restriction in
evening fluid intake may be enough in mild nocturia. Pharmacological
therapies are recommended after the failure of lifestyle changes and
behavioral treatments.30 So the increase in nocturia
severity negatively effects the patients’ quality of life and increased
urinary symptom scores may cause the failure of lifestyle changes and
behavioral treatments and may require additional treatments to lifestyle
changes in patients with moderate and severe nocturia. As all physicians
cannot evaluate patients with frequency-volume chart due to excessive
daily work-load in some regions; grading of nocturia may help for
management of patients in daily clinical practice.
Limitations: This study is not without limitations. Number of
participants from eight centers seem less compared to previous studies.
We believe that face-to-face design may overcome this limitation as more
standardized data driven for the study. We also did not evaluate for
sleep disorders specifically, as we aimed at looking for urological
disorders. However, isolated nocturia group in the present study may
reflect the sleep disorders as mentioned previously.
Conclusions: Nocturia has negative impacts on QoL of patients
and the impact rises with the increase of nocturia severity.
Nocturia-related pathophysiological factors may vary between mild,
moderate and severe nocturia groups. We believe that nocturia grading
with identification of subtypes may help for standardization of the
diagnostic and treatment approach as well as for the design of future
clinical trials.
Conflict of interest: none declared
Acknowledgements: none declared