An 18-year Follow-up Study on OSA in a Population-based Cohort

Our research team has established a polysomnography (PSG) quantified population-based paediatric sleep cohort in 2003 for a childhood OSA prevalence study. Subjects were recruited from 13 randomly selected primary schools. In each school, two randomly chosen classes from each grade were invited to participate. In the first phase, all parents of children in the randomly selected schools were invited to attend an education forum during which full explanation of the purpose and flow of the study was given. An envelope containing a validated parent proxy OSAS screening questionnaire and consent was then distributed to parents within a week after the forum. From our previous research, a composite symptom score (summation of the scores of these three questions) of 7 or more has 75.4% sensitivity and 80.5% specificity, compared with polysomnography, to detect OSAS among children aged 5-15 years who had attended our paediatric clinics. Children with a composite symptom score of less than 7 were assigned a computer-generated random number and were invited as a control group with a ratio of 1:2 in the second phase. All children belonging to the high risk of OSAS group and the randomly selected subjects at low risk of OSAS were invited to participate the baseline epidemiological study. In total 619 children aged 5-13 years underwent detailed assessments including anthropometric measurements, airway examination, ambulatory blood pressure recording and overnight PSG. 67 children had moderate-to-severe OSA (obstructive apnoea hypopnoea index, OAHI ≥5/h), 199 had mild OSA (OAHI 1 to <5/h), 103 were primary snorers (OAHI <1/h but snore ≥3 nights per week in the past 12 months) and 250 were normal controls (OAHI <1/h and snore <3 nights per week in the past 12 months).(1) All subjects from this original cohort will be invited to join this 18-year follow-up study to repeat the following data collection: questionnaires, anthropometric measurement, sleep study, 24-hour ambulatory blood pressure (ABP) measurement, echocardiography and neurocognitive assessment.

Inclusion criteria

• Subjects participants from the 2003 cohort

Exclusion criteria

• Neuromuscular disease
• Pathological central apnoea
• Severe chronic lung disease with documented hypoxaemia or awake oxygen saturation <92%
• Chronic respiratory failure (unrelated to OSA)
• Acquired upper airway disease/obstruction
• Craniofacial abnormalities (e.g. secondary to trauma and malignancy)

Other arrangement:

• Subjects who have any respiratory illness within 2 weeks of the scheduled follow-up visit will have their assessment re-arranged until they have fully recovered.
• Subjects taking medications that may affect sleep, upper airway patency or blood pressure (for example sedatives, stimulants, antihistamines, and cough medicine) within a week from recruitment will also be rescheduled to participate when they are free from medication use for at least 2 weeks.
• Subjects with hypertension and are on anti-hypertensive therapy are allowed to continue on their medication and the information will be obtained and recorded during data collection.