title: Seasonal trend of acute pelvic inflammatory disease.
abstract: OBJECTIVE
  Many infections follow a seasonal trend. Aim of our study was to check whether acute pelvic inflammatory disease (PID) follows a seasonal progress.
  
  
  METHODS
  In a retrospective study on 12,152 hospital records, 158 cases of acute pelvic inflammatory disease were identified. Periodogram analysis was applied to the date of pelvic inflammatory disease admission and to related environmental factors, such as temperature and photoperiod.
  
  
  RESULTS
  Pelvic inflammatory disease follows a seasonal rhythm with mean to peak variation of 23 % and maximal values in September (±37.2 days). The rhythm, more evident in married women, is related to the rhythm of temperature advanced by 2 months and of photoperiod advanced by 3 months. Cases of pelvic inflammatory disease are more frequent than expected in unmarried (36 vs. 17.3/34,626, p = 0.015), particularly divorced women 30-40 years of age.
  
  
  CONCLUSIONS
  Our study evidences a seasonal trend and confirms unmarried, particularly divorced status, as important risk factor for acute pelvic inflammatory disease.
authors.affiliation: Obstetrics and Gynaecology Unit, Department of Obstetrics Gynaecology and Paediatric, Azienda Policlinico of Modena, Via del Pozzo 71, 41121, Modena, Italy.
authors.forename: Anjeza
authors.initials: A
authors.lastname: Xholli
authors.forename: Marianna
authors.initials: M
authors.lastname: Cannoletta
authors.forename: Angelo
authors.initials: A
authors.lastname: Cagnacci
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D002940:Circadian Rhythm; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data* / Q000639:trends; D006801:Humans; D007558:Italy / Q000453:epidemiology; D000292:Pelvic Inflammatory Disease / Q000453:epidemiology* / Q000209:etiology; D017440:Photoperiod; D015995:Prevalence; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons; D012725:Sexual Behavior; D012959:Socioeconomic Factors; D055815:Young Adult