Serum retinol and airway obstruction.

The relation of serum retinol and carotenoids to airway obstruction was investigated in a population-based study. Respiratory symptoms and the pulmonary function of 83 white males were assessed in 1979 5 years after their blood had been drawn. Airway obstruction in 1979, defined as a forced expiratory volume in 1 second which was equal to or less than 75% of the forced vital capacity, was associated with a decreased 1974 level of serum retinol.