Total serum IgE and FEV1 by respiratory symptoms and obstructive lung disease in adults of a Norwegian community

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Abstract
The importance of total serum IgE level on lung function impairment has not been established in a general population. The aim of this cross-sectional community study was to examine the relationship between total serum IgE and level of lung function in adults, and whether this relationship differed by sex, age, smoking habits or by respiratory symptoms and disease status. A stratified random sample of 18-73 year old adults from the general population were invited to spirometry and serum analyses of total and specific IgE. Of 1512 subjects invited, 82% met and performed complete examinations. Increasing level of total serum IgE was related to reduced lung function (P < 0.01) given as sex, age, and height standardized residuals of one second forced expiratory volume (SFEV1). Subjects with total serum IgE in the highest vs the lowest tertile had a mean SFEV1 of -0.28, corresponding to age and height adjusted FEV1 differences of 120 and 150 mL in women and men, respectively. The relationship between IgE and lung function impairment did not differ significantly by sex, age or smoking habits. In subjects with obstructive lung disease increasing level of total serum IgE was more negatively associated with lung function level than in subjects with respiratory symptoms alone. No relationship was observed in asymptomatic subjects. This was confirmed in a multiple linear regression analysis adjusting for sex, age, smoking habits and lifetime smoking consumption showing that SFEV1 was predicted by an interaction between total serum IgE level and symptom and disease status (P < 0.01). This interaction remained after excluding subjects (n = 105) having specific IgE antibodies. Increasing total serum IgE level was associated with progressively lower lung function in a general adult population after taking other predictors of impaired spirometric lung function into account, though dependent on the subjects' respiratory symptom and disease status. Variation in prevalences of respiratory symptoms and obstructive lung disease in previous examined populations may thus explain conflicting observations of the association between total IgE and airflow impairment.