title: White blood cell count and mortality in the Baltimore Longitudinal Study of Aging.
abstract: OBJECTIVE
  We investigated the secular trend in white blood cell (WBC) count and the relationship between WBC count and mortality between 1958 and 2002.
  
  
  BACKGROUND
  The WBC count is a clinical marker of inflammation and a strong predictor of mortality. Limited data exist on the WBC count secular trend and the relationship between WBC and mortality.
  
  
  METHODS
  One thousand eighty-three women and 1,720 men were evaluated longitudinally in the Baltimore Longitudinal Study of Aging. Blood samples and medical information were collected at the study entry and every 2 years during follow-up visits. The WBC count and all-cause, cardiovascular, and cancer mortality were assessed.
  
  
  RESULTS
  A downward trend in WBC count was observed from 1958 to 2002. The secular downward trend was independent of age, gender, race, smoking, body mass index, and physical activity. The WBC count was nonlinearly associated with all-cause mortality and almost linearly associated with cardiovascular mortality. Participants with baseline WBC <3,500 cells/mm3 and WBC >6,000 cells/mm3 had higher mortality than those with 3,500 to 6,000 WBC/mm3. Within each WBC group, age-adjusted mortality rates declined in successive cohorts from the 1960s to the 1990s. Participants who died had higher WBC than those who survived, and the difference was statistically significant within 5 years before death.
  
  
  CONCLUSIONS
  Our study provides evidence for a secular downward trend in WBC count over the period from 1958 to 2002. Higher WBC counts are associated with higher mortality in successive cohorts. We found no evidence that the decline of age-specific mortality rates that occurred from 1960 to 2000 was attributable to a secular downward trend in WBC.
authors.affiliation: Longitudinal Studies Section, Clinical Research Branch, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21225, USA. ruggieroc07@hotmail.it
authors.forename: Carmelinda
authors.initials: C
authors.lastname: Ruggiero
authors.forename: E Jeffrey
authors.initials: EJ
authors.lastname: Metter
authors.forename: Antonio
authors.initials: A
authors.lastname: Cherubini
authors.forename: Marcello
authors.initials: M
authors.lastname: Maggio
authors.forename: Ranjan
authors.initials: R
authors.lastname: Sen
authors.forename: Samer S
authors.initials: SS
authors.lastname: Najjar
authors.forename: Gwen B
authors.initials: GB
authors.lastname: Windham
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ble
authors.forename: Umberto
authors.initials: U
authors.lastname: Senin
authors.forename: Luigi
authors.initials: L
authors.lastname: Ferrucci
mesh_terms: D015142:Baltimore / Q000453:epidemiology; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000097:blood / Q000401:mortality; D002423:Cause of Death; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D008137:Longitudinal Studies; D008297:Male; D009026:Mortality; D016016:Proportional Hazards Models; D016019:Survival Analysis