The Association Between Sleep Duration and Sleep Disorders and Proteinuria in Children

200 children aged 2-18 years that will be referred to the Sleep Disorders Center for overnight polysomnography due to suspected sleep disordered breathing or PLMD will be recruited to the study during their first visit in the sleep clinic. During that study, an informed consent will be completed by the parents. Data on weekdays and weekends sleep duration as well as personal and family history of kidney disease will be collected.

Exclusion criteria:1. Known renal disease; 2. diabetes mellitus; 3. current use of ACE inhibitors or angiotensin receptor blockers; 4. neuromuscular disorders or craniofacial abnormalities; 5. syndromic conditions.

All participants will undergo physical examination. Weight and height will be measured, and body mass index (BMI) z-score will be calculated.

Blood pressure will be measured on the first visit in the sleep clinic by a trained physician as specified in recent guidelines. 19

Overnight polysomnography will be carried out in the Sleep Disorders Laboratory and the following signals will be recorded: electroencephalogram (EEG; C3/M2, C2/M1, O1/M2, O2/M1); right and left oculogram; submental and tibial electromyogram; body position; electrocardiogram; thoracic and abdominal wall motion; oronasal airflow (three-pronged thermistor and nasal pressure transducer); and oxygen saturation of hemoglobin (SpO2). Arousals, sleep stages and respiratory events will be scored, and polysomnography indices will be defined according to the recent American Academy of Sleep Medicine recommendations . 20

First void urine samples will be collected in a sterile cup the morning following the polysomnography (6:00-7:00 am). For each sample urinalysis, protein/creatinine and albumin/creatinine will be measured. Urinary albumin and protein excretion will be the primary outcome measure. Proteinuria will be defined as protein/creatinine greater than 0.2 and albuminuria will be defined as albumin/creatinine above age-adjusted limits Children who will be diagnosed with moderate-severe OSA will be referred to an ENT surgeon for adenotonsillectomy, the first line of treatment in pediatric OSA. Six to 10 weeks following surgery, these children will be requested to undergo additional PSG evaluation. First void urine samples will be collected the following morning.

In addition- 100 children referred to the pediatric nephrology clinic due to asymptomatic albuminuria/proteinuria will be recruited. Parents will be required to complete a designated sleep questionnaire that includes items on sleep duration, SDB and RLS symptoms. Exclusion criteria, as described above for the entire cohort, will also apply to this subpopulation.

Informed consent will be completed by the parents.