title: Dehydration as a Possible Cause of Monthly Variation in the Incidence of Venous Thromboembolism.
abstract: BACKGROUND
  Monthly or seasonal changes in the incidence of venous thromboembolism (VTE) were previously reported; however, the mechanism of such variability is not completely understood.
  
  
  METHODS
  In the present retrospective single-center analysis, consecutive patients with proximal deep vein thrombosis and/or pulmonary embolism (PE) diagnosed between January 2009 and December 2013 were evaluated.
  
  
  RESULTS
  The study population included 1496 patients, 48% men, mean age 63 ± 18 years. Most (82%) cases with VTE were provoked and 39% of patients had active cancer. Four months of peak incidence (3, 7, 10 and 11) were compared with 4 months of the lowest incidence (4, 5, 6, and 12), showing a significant difference in VTE numbers (597 vs 405 cases/year, P = 0.001). In all subgroup analyses, including gender, provoked or unprovoked event and presence or absence of cancer, significant differences between the months of peak and lowest incidence remained. Blood urea nitrogen (BUN)-creatinine ratio was significantly higher in all cases in the peak incidence group compared to the lowest incidence group (24 ± 1.5 vs 21 ± 1.6, P = 0.03). In patients with unprovoked VTE (n = 269), levels of BUN and hematocrit were significantly increased in the peak incidence group compared to lowest incidence group (19.5 ± 0.8 mg/dL vs 16 ± 1.1 mg/dL, P = 0.03; 39.2 ± 0.3% vs 37.4 ± 0.5%, P = 0.01, respectively).
  
  
  CONCLUSIONS
  The current study demonstrates that occurrence of VTE exhibits monthly variation also existing in patients with provoked events and even in those with cancer. Dehydration is suggested as a potential explanation to the month-related variation in incidence of VTE.
authors.affiliation: Department of Hematology, Thrombosis and Hemostasis Unit, Rambam Health Care Campus, Haifa, Israel.
authors.forename: Saad
authors.initials: S
authors.lastname: Elias
authors.affiliation: Department of Hematology, Thrombosis and Hemostasis Unit, Rambam Health Care Campus, Haifa, Israel The Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel.
authors.forename: Ron
authors.initials: R
authors.lastname: Hoffman
authors.affiliation: Department of Hematology, Thrombosis and Hemostasis Unit, Rambam Health Care Campus, Haifa, Israel.
authors.forename: Gleb
authors.initials: G
authors.lastname: Saharov
authors.affiliation: Department of Hematology, Thrombosis and Hemostasis Unit, Rambam Health Care Campus, Haifa, Israel The Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Brenner
authors.affiliation: Department of Hematology, Thrombosis and Hemostasis Unit, Rambam Health Care Campus, Haifa, Israel The Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel ynadir@netvision.net.il.
authors.forename: Yona
authors.initials: Y
authors.lastname: Nadir
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003681:Dehydration / Q000150:complications*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications; D011655:Pulmonary Embolism / Q000453:epidemiology / Q000209:etiology; D012189:Retrospective Studies; D012307:Risk Factors; D054556:Venous Thromboembolism / Q000453:epidemiology / Q000209:etiology*; D020246:Venous Thrombosis / Q000453:epidemiology / Q000209:etiology
keywords: DVT; PE; VTE; dehydration; month; season