Temporal change in the prevalence of respiratory symptoms and obstructive airways disease 1993-2001

Background There has been little available information regarding secular changes in the prevalence of respiratory symptoms since the mid-1990s.

Aim To examine changes in the prevalence of respiratory symptoms for 1993-2001.

Design of study A series of postal questionnaire surveys.

Setting Two general practice populations, including all age groups.

Method Four postal respiratory questionnaire surveys were conducted between 1993 and 2001. Subjects who replied to two or more surveys (8058 adults and 2350 children) were included in the main analyses. Validated scoring systems were used to define obstructive airways disease in adults and asthma in children.

Results Over the 8-year observation period there were increases among adults in the crude prevalence of wheeze, being woken by cough, receipt of current asthma medication, and of obstructive airways disease, compared with decreases in children for wheeze, night cough, asthma attacks, and asthma. For adults, adjusted odds ratios per year of secular increase were 1.03 (95% confidence interval [Cl] = 1.02 to 1.03) for wheeze, 1.03 (95% Cl = 1.02 to 1.03) for being woken by cough, 1.03 (95% Cl = 1.02 to 1.04) for asthma medication, and 1.02 (95% Cl = 1.01 to 1.03) for obstructive airways disease. These increases were greater in those aged over 44 years, in males, and in those without a family history of asthma or a history of hayfever or eczema. Corresponding decreases for children were 0.94 (95% Cl = 0.92 to 0.97) for wheeze, 0.93 (95% Cl = 0.91 to 0.96) for night cough, 0.93 (95% Cl = 0.90 to 0.95) for asthma attacks and 0.98 (95% Cl = 0.95 to 1.00) for asthma.

Conclusion The increases found in adults are more likely to be due to chronic obstructive pulmonary disease (COPD) than asthma. This is supported by the decreases in symptom and asthma prevalence in children.