Influence of demographic and disease related factors on the degree of distress associated with symptoms and restrictions on daily living due to asthma in six countries.

To investigate the influence of demographic and physiological variables on the degree of distress associated with asthma, 124 patients were recruited from six countries. All patients responded to 76 items relating to symptoms and impacts of asthma on daily living by marking a 10 cm visual analogue scale (VAS) to indicate the degree of distress associated with any particular item. The influence of three factors, age, sex and forced expiratory volume in one second (FEV1), on these VAS scores was investigated. Differences between patients accounted for 13.4% of the total variance (sum of squares) in VAS scores. There were no significant effects of sex, age or FEV1 on VAS score (p greater than 0.05 in each case). The separate proportionate contribution of each of these three factors to the total variance in item scores ranged from 0.02% (FEV1) to 0.2% (sex). There were significant differences between the mean VAS scores from the six countries (p less than 0.01) but these differences contributed to only 3.6% of the total variance in the measured VAS scores. We conclude that demographic and disease related factors account for very little of the differences in the degree of distress that patients attach to the symptoms and effects of asthma. We suggest that it is possible to make meaningful comparisons between countries of the impact of asthma on patients' lives.