[Vocal fold nodules. Risk factors in teachers. A case control study design].
Vocal nodules are structural lesions very common amongst professional voice users such as teachers. We have studied the risk factors that predispose the development of vocal nodules in teachers. Two hundred and forty-two teachers were selected: 120 with vocal nodules and 120 with normal vocal folds. Professional and personal factors as well as classroom environment were studied. A complete evaluation of the voice was performed, aerodynamic measures, tone and extension of the voice, acoustic analysis, perceptual evaluation of the voice as well as a videolaryngostroboscopy which was definitive in the diagnosis. Younger teachers with less years of teaching experience a greater have tendency to develop vocal nodules than the rest. Class-room's dryness, loudness and echo are correlated with the pathological group. The most relevant personal factors in the pathological group were previous vocal pathology, laryngeal surgery, nasal surgery and gastroesophageal reflux. Vocal intensity and vocal frequency ranks were shorter in the pathological group. We could also see that, fonatory flow was less effective in the pathological group.