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Lars-Gunnar Larsson


SNORING AND OTHER SYMPTOMS RELATED TO OBSTRUCTIVE SLEEP APNEA; prevalence, risk factors, and relation to respiratory disorders - The Obstructive Lung Disease in Northern Sweden Study III

Lars-Gunnar Larsson

These studies are a part of the Obstructive Lung Disease in Northern Sweden Studies (OLIN), an epidemiological research program in Northern Sweden. The aim of this thesis was to examine the prevalence of symptoms related to Obstructive Sleep Apnea Syndrome (OSAS) in Norrbotten, their relation to lung function, respiratory diseases including bronchitis, asthma and rhinitis, to examine risk factors, gender differences, and to the extent to which subjects with symptoms related to OSAS have received attention in the public health care system. A further aim was to validate whether snoring as a problem predicts obstructive sleep apnea (OSA).

In 1991 a questionnaire was sent by mail to a bronchitic cohort where 450 of 523 (86%) participated, and to a respiratory healthy control group where 529 of 625 (85%) participated in three age groups, 41-42 y, 56-57 y, and 71-72 y. The survey was followed by lung function tests and clinical examinations (n=579). Overnight sleep recordings were done in subjects reporting snoring as a problem (n=52). A second survey by mail was performed in 1992 in a representative sample of men and women aged 20-69 y, and 4648 of 5424 (86%) subjects responded. The OLIN questionnaire about respiratory symptoms and diseases, smoking habits, and profession with additional questions about sleep disturbances was used in the two surveys. The studies were performed in Norrbotten, which is the northernmost province of Sweden.

In the bronchitic cohort the prevalence of symptoms related to OSAS was higher than in the control group, snoring as a problem 23 vs. 12%, witnessed apneas 18 vs. 8.3%, nod off 16 vs. 7.0%, and not rested after a full nights sleep, 33 vs. 28% respectively. Subjects with recurrent wheeze, chronic productive cough, or sputum production reported snoring as a problem and witnessed apneas twice as often as subjects in the healthy cohort. Bronchitic symptoms but not lung function impairment was associated with snoring as a problem or witnessed apneas. The sleep studies showed that subjects with bronchitis were found to have obstructive sleep apnea twice as often as subjects without respiratory symptoms. The minimum prevalence for OSA (AHI ³ 10) with concomitant daytime sleepiness (OSAS) was 5.4% in subjects with bronchitic symptoms and 2.3% in the respiratory healthy.

In the population study 11% (15 in men, 6.7% in women) reported snoring as a problem. The prevalence increased with age with a peak prevalence in men at 55-59 y (28%), and in women at 60-64 y (14%), while declined in the elderly. Relatives' concerned about witnessed sleep apneas was reported by 6.8% (11% in men, 2.4% in women). The age distribution of witnessed apneas was the same as in snoring with peaks in the same age groups, 21% in men aged 55-59 y, and 6.5% in women aged 60-64 y. Daytime sleepiness was more common in subjects reporting snoring as a problem, especially in women, in whom not rested after a full night sleep was reported by 50% vs. 40% among men. Snoring as a problem was more common in subjects with concomitant respiratory symptoms: among subjects with chronic bronchitis 26%, physician-diagnosed asthma 20%, and rhinitis 15% vs. 10% in subjects without these disorders. Age, male gender, current smoking, chronic bronchitis, asthma, and rhinitis were independently associated with snoring as a problem, as analysed by multiple logistic regression.

Between 1990 and 2000, 3955 subjects (2991 men, 964 women) aged 20-69 were referred to the Department of Respiratory Medicine in Boden/Sunderby Hospital for sleep studies due to symptoms related to OSAS. The estimated prevalence of snoring as a problem or witnessed apneas in our study was 18% in men, and 7.4% in women. By presuming that the prevalence has been stable, we can estimate that during a 10-year period approximately 20% of men and 16% of women with these symptoms have been referred for sleep studies. According to prevalence of symptoms in our study, women with snoring as a problem or witnessed sleep apneas were less likely to have been referred for a sleep study than men, although they had reported more daytime sleepiness symptoms.

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