The causes of the worldwide increase in asthma seen during the last decades remain largely unexplained, but lifestyle and diet are suggested to play important roles. In this follow up of a large-scale population sample in Sweden, we wanted to identify modifiable risk factors for the cumulative incidence over a 13-year follow-up period. In 1990, a self-administered questionnaire was completed by 12,560 individuals from three age groups (16, 30-39 and 60-69 years of age) in two counties of Sweden. In 2003, the eligible subjects (n = 11,282) were sent a new postal questionnaire. In total 8150 (response rate 73%) answered the questionnaire. The prevalence of asthma in 2003 had increased in all ages. In the young adults, the asthma prevalence rose from 11.3% in 1990 to 25.0% in 2003. Adult asthma onset was identified in 791 of the participants. Smoking [RR (95% CI) = 1.37 (1.12-1.68)], BMI [1.49 (1.25-1.77 per inter quartile range)], and nocturnal gastro-oesophageal reflux (GOR) [2.16 (1.72-2.72)] were significant independent risk factors for the cumulative incidence of asthma. The impact of risk factors differed between the age groups where BMI and GOR had a significantly higher impact in the middle aged and the elderly (p < 0.05). High consumption of fruit and fish was protective especially in the elderly [0.52 (0.35-0.77)]. No significant difference was found in the impact of risk factors between men and women. Weight loss, smoking cessation and a diet rich in fruit and fish may be of importance in preventing onset of adult asthma.

Whether long-term oxygen therapy (LTOT) improves quality of life in chronic hypoxaemia has been questioned. LTOT with an oxygen concentrator (C/C) and gas cylinders for ambulation is considered cumbersome compared to mobile liquid oxygen equipment (L). The hypothesis for this study was that LTOT with liquid oxygen treatment (L) improves patients' health-related quality of life, but that it is also more expensive compared to concentrator (C/C) treatment. A prospective, randomized multicentre trial comparing C/C with L for LTOT was conducted during a six-month period. Fifty-one patients (29 on L and 22 on C/C) with chronic hypoxaemia, regularly active outside the home, participated in the study initially. Costs for oxygen were obtained from the pharmacies. Patient diaries and telephone contacts with members of the healthcare sector were used to estimate costs. Health-related quality of life was measured by the Sickness Impact Profile (SIP) and the EuroQol, instruments at the start and after 6 months. The average total cost per patient for group C/C for the six-month period was US$1,310, and for group L it was US$4,950. Health-related quality of life measured by the SIP instrument showed significant differences in favour of group L in the categories/dimensions of physical function, body care, ambulation, social interaction and total SIP score. In conclusion, liquid-oxygen treatment was more expensive compared to concentrator treatment. However, treatment effects showed that liquid oxygen had a better impact on quality of life.

Background -Considerable variation exists in the use of antiasthmatic drugs in different counties in Sweden. The reasons for this variation are unknown. A study was performed to determine if there is an association between sales of antiasthmatic drugs and the prevalence of obstructive airway diseases in two adjoining Swedish counties. Method -The prevalence of asthmaassociated symptoms in the county of Jamtland where there is high drug use, and the county of Gavleborg where it is lower, was assessed in 1990 by a postal questionnaire answered by 11 300 subjects. Three age groups were included: all 16 year olds, 13% of those aged 30-39 years, and 13% of 60-69 year olds. A total of 2100 subjects reporting airway symptoms in a questionnaire and 450 asymptomatic controls were further investigated at an interview with lung function tests and, in 500 cases, with a methacholine challenge. Asthma was diagnosed in subjects reporting a typical history or repeated episodes of dyspnoea and wheezing, or dry cough combined with reversibility in FEV,, variability in peak expiratory flow, or a PC20 value of < 4 mg/ml. Results -The prevalence of current asthma was close to 8% in all age groups in Jamtland and significantly lower (close to 6%) in all age groups in the warmer, more industrialised and more densely populated county of Gavleborg. A gender difference with a higher prevalence in women was found in Gavleborg but not in Jamtland. There was no significant difference in the use of inhaled P2 stimulants among subjects with asthma in the two counties. Inhaled steroids were used more often in Jamtland. However, they were used regularly by fewer than 10% of asthmatic subjects in the two younger age groups. Conclusion -The differences in the use of antiasthmatic drugs in these two counties reflect a difference in the prevalence of obstructive airway disease. (Thorax 1994;49:41-49)

Participants with low health-related quality of life at baseline were more likely to report having developed asthma 12 years later.