title: Pulmonary embolism: Does the seasonal effect depend on age? A 12-year nationwide analysis of hospitalization and mortality.
abstract: BACKGROUND
  Circannual variations in the incidence and mortality of pulmonary embolism (PE) have been previously described although conflicting observations have been reported. However, the association between age and seasonal variations of incidence and mortality rates is not established. This nationwide study aimed to assess the seasonal pattern in hospitalizations and mortality for PE along with the effect of age.
  
  
  METHODS
  Comprehensive records from the French hospital discharge databases between 2002 and 2013 and death certificates between 2000 and 2010 were used. For each outcome and separately for each sex, monthly event counts were analyzed using quasi-Poisson models with tensor-products of regression splines, including a seasonal component and controlling for the underlying time trend, age of patients and population size changes.
  
  
  RESULTS
  During the period studied, 599,432 patients with PE were hospitalized and 150,404 death certificates mentioned a PE. Compared with summer months, the winter peak was associated with 25% increasing rates in hospitalizations and mortality. The rates ratio of hospitalizations between the winter peak and the summer trough increased with age. The winter excess of incidence raised from 10%, IC 95% [5-16] in 30-year-old men to 33% [31-35] in 75year-old men. In the same way, the incidences at the peak time was 13% [9-18] and 34% [31-36] higher in 30 and 75-year-old women respectively.
  
  
  CONCLUSIONS
  Based on large nationwide study, our study showed a clear seasonal pattern both on PE incidence and mortality. In addition, our data supported an association of age on the PE seasonal variations.
authors.affiliation: Non-communicable diseases and trauma direction, The French Public Health Agency, Saint-Maurice, France. Electronic address: valerie.olie@santepubliquefrance.fr.
authors.forename: V
authors.initials: V
authors.lastname: Olié
authors.affiliation: Non-communicable diseases and trauma direction, The French Public Health Agency, Saint-Maurice, France.
authors.forename: C
authors.initials: C
authors.lastname: Bonaldi
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006760:Hospitalization; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010351:Patient Discharge; D011156:Population Density; D011655:Pulmonary Embolism / Q000453:epidemiology* / Q000401:mortality; D012621:Seasons
keywords: Age; Hospitalization; Mortality; Pulmonary embolism; Seasons