Study protocol
A total of 65 persons signed an informed consent, 20 persons were
excluded (never started (n = 17), night shift (n = 1), failed to follow
the instructions for urine collections (n = 2)) and thus a total of 45
persons were eligible for analysis. Demographic data were collected.
Within a period of six weeks, two extended urine collections were
obtained during two non-consecutive 24-hour periods to determine
diuresis rate and renal functions. For this, participants were asked to
collect 5 daytime 3 and nighttime urine samples at fixed time intervals
over 24 hours. Voided volume at the time of sample collection, as well
as volumes of any interim micturition, were recorded. During the first
extended urine collection, participants also had to collect all daytime
and nighttime urine in a daytime and nighttime container. Urinary
concentration of osmolality, creatinine and sodium were determined for
all urine samples and for both urine containers. Participants had to
respect directives regarding the intake of fluids and food during both
study days (drink 1.5-2 liters water and do not drink more than 2 units
of alcohol per day; avoid salting their food and eating aperitif snacks,
sauces, fast food and ready-made meals).
Furthermore, patients were asked to keep track of their movements and
were requested to give an indication of what they had done the most
during a period of time of one hour. Movement/position was divided into
five categories. 0 was equivalent of having laid down the most that
hour. 1 meant that the participant had been sat down for most of the
hour. 2 stood for standing up. 3 was allocated to walking as the
majority movement of the hour. 4 was given if the patient had performed
more intense activity during that hour i.e. running, cycling etc.
The study was carried out in conformity with the Declaration of
Helsinki. The Ghent University Hospital Review Board approved the study
(EC/2013/802) and all participants gave written consent