THE PREVALENCE OF CLINICALLY SIGNIFICANT SLEEP-APNEA SYNDROME IN THE NETHERLANDS

Background-Figures for the prevalence of sleep apnoea syndrome range f rom 0.3% to 8.5%. These widely ranged estimates are probably due to di fferences in the definitions used, study designs, and study population s. A study was undertaken to determine the lower limit of the prevalen ce of clinically significant sleep apnoea syndrome. Methods-A cross se ctional survey by postal questionnaire was carried out in a general pr actice of a small town in which three doctors serve 93% of its populat ion of 6747 inhabitants of all ages. All men aged 35 and over and wome n aged 50 and over were invited to fill in a specially designed questi onnaire on snoring and sleep. All men and women whose answers suggeste d the possible occurrence of sleep apnoea were invited to undergo furt her investigation. Oronasal thermistry was performed in the subjects' homes and the results were scored to provide an apnoea index (AI). Tho se subjects with an AI of 85 were referred to a sleep laboratory for i nvestigation by polysomnography. Results-Of the 2466 questionnaires is sued, 2182 (88.5%) were completed and returned. The occurrence during the previous three months of regular snoring, together with daytime sl eepiness and/or partners' observation of interruptions in breathing at night, was reported by 194 subjects (169 men, 25 women). In 173 subje cts oronasal thermistry applied in their homes provided satisfactory r ecordings and, of these, 24 men and one woman had an AI of greater tha n or equal to 5. Analysis of the polysomnographic findings showed that 14 men and one woman met the criteria for sleep apnoea syndrome. Scru tiny of their case records disclosed that in seven men this was clinic ally significant. Conclusions-Our findings suggest that the prevalence of clinically significant sleep apnoea syndrome in men aged 35 and ov er is at least 0.45%. Extrapolation to the population of the Netherlan ds suggests that at least 16 000 men suffer from sleep apnoea syndrome that should be relieved by medical care. A large proportion of these subjects remains to be diagnosed.