Respiratory symptoms, lung function, and bone mineral density in a comprehensive population study: The Nord-Trøndelag Health Study 1995-97, The Bronchial Obstruction in Nord-Trøndelag Study

Abstract

The prevalence of respiratory symptoms and diseases like asthma and chronic obstructive pulmonary disease (COPD), seem to have increased the last decades. The reason for the increase in asthma related symptoms and allergy is uncertain. Some, but not all, of this increase might be ascribed to lowered threshold for use of the diagnosis by medical doctors, change in diagnostic criteria, and increased awareness of symptoms in the population. Studies have indicated that increased prevalence might be explained by a reduction during the last decades in exposure to environmental factors in infancy, These factors are supposed to stimulate the change from Th-2 to TH-1 helper cells (hygiene hypothesis), but even low level of allergen exposure seems to contribute to increase in risk for allergy. The increase in COPD in developed countries is closely related to the smoking pattern during the last two to four decades, and the increased therefore, is mainly seen in women. Further, studies have indicated that women are more vulnerable for the deleterious effects of tobacco smoking than men are; if this is true the current smoking pattern with increased female smoking, is worrying.