Several studies have identified obesity as a risk factor for asthma in both children and adults. An increased prevalence of asthma in subjects with gastro-oesophageal reflux (GOR) and obstructive sleep apnoea syndrome has also been reported. The aim of this investigation was to study obesity, nocturnal GOR and snoring as independent risk factors for onset of asthma and respiratory symptoms in a Nordic population.In a 5–10 yr follow-up study of the European Community Respiratory Health Survey in Iceland, Norway, Denmark, Sweden and Estonia, a postal questionnaire was sent to previous respondents.A total of 16,191 participants responded to the questionnaire. Reported onset of asthma, wheeze and night-time symptoms as well as nocturnal GOR and habitual snoring increased in prevalence along with the increase in body mass index (BMI). After adjusting for nocturnal GOR, habitual snoring and other confounders, obesity (BMI >30) remained significantly related to the onset of asthma, wheeze and night-time symptoms. Nocturnal GOR was independently related to the onset of asthma and in addition, both nocturnal GOR and habitual snoring were independently related to onset of wheeze and night-time symptoms.This study adds evidence to an independent relationship between obesity, nocturnal gastro-oesophageal reflux and habitual snoring and the onset of asthma and respiratory symptoms in adults.

The impact of active smoking, passive smoking, and obesity on habitual snoring in the population is mainly unknown. We aimed to study the relationship of habitual snoring with active and passive tobacco smoking in a population-based sample. A total of 15,555 of 21,802 (71%) randomly selected men and women aged 25-54 years from Iceland, Estonia, Denmark, Norway, and Sweden answered a postal questionnaire. Habitual snoring, defined as loud and disturbing snoring at least 3 nights a week, was more prevalent among current smokers (24.0%, p < 0.0001) and ex-smokers (20.3%, p < 0.0001) than in never-smokers (13.7%). Snoring was also more prevalent in never-smokers exposed to passive smoking at home on a daily basis than in never-smokers without this exposure (19.8% vs. 13.3%, p < 0.0001). The frequency of habitual snoring increased with the amount of tobacco smoked. Active smoking and passive smoking were related to snoring, independent of obesity, sex, center, and age. Ever smoking accounted for 17.1% of the attributable risk of habitual snoring, obesity (body mass index > or = 30 kg/m(2)) for 4.3%, and passive smoking for 2.2%. Smoking, both current and ex-smoking, is a major contributor to habitual snoring in the general population. Passive smoking is a previously unrecognized risk factor for snoring among adults.