title: Snoring, mouth-breathing, and apnea trajectories in a population-based cohort followed from infancy to 81 months: a cluster analysis.
abstract: OBJECTIVE
  The objective of this study was to characterize phenotypes of sleep disordered breathing (SDB) in early childhood that clinicians may find useful while monitoring symptom progression and associated SDB morbidity.
  
  
  METHODS
  We performed a cluster analysis of SDB's primary symptoms: snoring, mouth-breathing, and apnea. Parents in the Avon Longitudinal Study of Parents and Children (ALSPAC) reported SDB symptoms by questionnaire for their child at 6, 18, 30, 42, 57, 69, and 81 months of age. Participants were those from the original cohort exclusive of children with congental or other medical conditions predisposing growth aberrations or respiratory problems (i.e. cleft palate, heart surgery and associated conditions, genetic syndromes-primarily Down's, cancer or kidney conditions, celiac disease, congenital adrenal hyperplasia), missing SDB measures for ≥ 2 timepoints, or missing birth length plus 2 subsequent height measures.
  
  
  RESULTS
  Five clusters emerged from 10,441 children and were characterized according to patterns of mean severity of SDB symptoms over time. "Normals" (50%) were asymptomatic throughout. The "late snores and mouth-breathing" cluster (20%) remained asymptomatic until 4 years old. The "early snores" (10%) and "early apnea" (10%) clusters had peak symptoms at 6 and 18 months, respectively. In "all SDB after infancy" (10%), symptoms peaked from 30 to 42 months and remained elevated. Exploratory analyses found that "early snores" were significantly shorter than "normals." Associations with tonsillectomies and wheezing frequency supported external validation.
  
  
  CONCLUSIONS
  Cluster analysis has elucidated the dynamic multi-symptom expression of SDB. The utility of cluster analysis will be evaluated in future analyses to predict growth, cognition and behavior outcomes.
authors.affiliation: Department of Epidemiology and Population Health, Montefiore Medical Center/Albert Einstein College of Medicine, 111 East 210th Street, Bronx, NY 10467, United States. kfreeman@montefiore.org
authors.forename: Katherine
authors.initials: K
authors.lastname: Freeman
authors.forename: Karen
authors.initials: K
authors.lastname: Bonuck
mesh_terms: D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods; D009058:Mouth Breathing / Q000175:diagnosis / Q000453:epidemiology*; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution; D012891:Sleep Apnea Syndromes / Q000175:diagnosis / Q000453:epidemiology*; D012913:Snoring / Q000175:diagnosis / Q000453:epidemiology*; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology