title: Time series analysis of age related cataract hospitalizations and phacoemulsification.
abstract: BACKGROUND
  Cataract surgery remains a commonly performed elective surgical procedure in the aging and the elderly. The purpose of this study was to utilize time series methodology to determine the temporal and seasonal variations and the strength of the seasonality in age-related (senile) cataract hospitalizations and phacoemulsification surgeries.
  
  
  METHODS
  A retrospective, cross-sectional time series analysis was used to assess the presence and strength of seasonal and temporal patterns of age-related cataract hospitalizations and phacoemulsification surgeries from April 1, 1991 to March 31, 2002. Hospital admission rates for senile cataract (n = 70,281) and phacoemulsification (n = 556,431) were examined to determine monthly rates of hospitalization per 100,000 population. Time series methodology was then applied to the monthly aggregates.
  
  
  RESULTS
  During the study period, age-related cataract hospitalizations in Ontario have declined from approximately 40 per 100,000 to only one per 100,000. Meanwhile, the use of phacoemulsification procedures has risen dramatically. The study found evidence of biannual peaks in both procedures during the spring and autumn months, and summer and winter troughs. Statistical analysis revealed significant overall seasonal patterns for both age-related cataract hospitalizations and phacoemulsifications (p < 0.01).
  
  
  CONCLUSIONS
  This study illustrates the decline in age-related cataract hospitalizations in Ontario resulting from the shift to outpatient phacoemulsification surgery, and demonstrates the presence of biannual peaks (a characteristic indicative of seasonality), in hospitalization and phacoemulsification during the spring and autumn throughout the study period.
authors.affiliation: Primary Care Research Unit, Sunnybrook and Women's College Health Sciences Centre, Toronto, ON, M4N 3M5, Canada. alan.leong@utoronto.ca
authors.forename: Alan M
authors.initials: AM
authors.lastname: Leong
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Crighton
authors.forename: Rahim
authors.initials: R
authors.lastname: Moineddin
authors.forename: Muhammad
authors.initials: M
authors.lastname: Mamdani
authors.forename: Ross E G
authors.initials: RE
authors.lastname: Upshur
mesh_terms: D000375:Aging; D000553:Ambulatory Care / Q000706:statistics & numerical data / Q000639:trends; D002386:Cataract / Q000209:etiology*; D002387:Cataract Extraction / Q000706:statistics & numerical data* / Q000639:trends; D003430:Cross-Sectional Studies; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data* / Q000639:trends; D006801:Humans; D008297:Male; D018918:Phacoemulsification / Q000706:statistics & numerical data* / Q000639:trends; D012189:Retrospective Studies; D012621:Seasons; D013997:Time Factors