title: Clinical review: Endogenous testosterone and mortality in men: a systematic review and meta-analysis.
abstract: BACKGROUND
  Low testosterone levels have been associated with outcomes that reduce survival in men.
  
  
  OBJECTIVE
  Our objective was to perform a systematic review and meta-analysis of published studies to evaluate the association between endogenous testosterone and mortality.
  
  
  METHODS
  Data sources included MEDLINE (1966 to December 2010), EMBASE (1988 to December 2010), and reference lists.
  
  
  METHODS
  Eligible studies were published English-language observational studies of men that reported the association between endogenous testosterone and all-cause or cardiovascular disease (CVD) mortality. A two-stage process was used for study selection. 1) Working independently and in duplicate, reviewers screened a subset (10%) of abstracts. Results indicated 96% agreement, and thereafter, abstract screening was conducted in singlicate. 2) All full-text publications were reviewed independently and in duplicate for eligibility.
  
  
  METHODS
  Reviewers working independently and in duplicate determined methodological quality of studies and extracted descriptive, quality, and outcome data.
  
  
  RESULTS
  Of 820 studies identified, 21 were included in the systematic review, and 12 were eligible for meta-analysis [n = 11 studies of all-cause mortality (16,184 subjects); n = 7 studies of CVD mortality (11,831 subjects)]. Subject mean age and testosterone level were 61 yr and 487 ng/dl, respectively, and mean follow-up time was 9.7 yr. Between-study heterogeneity was observed among studies of all-cause (P < .001) and CVD mortality (P = 0.06), limiting the ability to provide valid summary estimates. Heterogeneity in all-cause mortality (higher relative risks) was observed in studies that included older subjects (P = 0.020), reported lower testosterone levels (P = 0.018), followed subjects for a shorter time period (P = 0.010), and sampled blood throughout the day (P = 0.030).
  
  
  CONCLUSIONS
  Low endogenous testosterone levels are associated with increased risk of all-cause and CVD death in community-based studies of men, but considerable between-study heterogeneity, which was related to study and subject characteristics, suggests that effects are driven by differences between cohorts (e.g. in underlying health status).
authors.affiliation: Department of Epidemiology, New England Research Institutes, Inc, Watertown, Massachusetts 02472, USA. aaraujo@neriscience.com
authors.forename: Andre B
authors.initials: AB
authors.lastname: Araujo
authors.forename: Julia M
authors.initials: JM
authors.lastname: Dixon
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Suarez
authors.forename: M Hassan
authors.initials: MH
authors.lastname: Murad
authors.forename: Lin T
authors.initials: LT
authors.lastname: Guey
authors.forename: Gary A
authors.initials: GA
authors.lastname: Wittert
mesh_terms: D000328:Adult; D000368:Aged; D006801:Humans; D008297:Male; D008875:Middle Aged; D000367:Age Factors; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000401:mortality; D002423:Cause of Death; D009026:Mortality / Q000639:trends; D018570:Risk Assessment; D012907:Smoking / Q000009:adverse effects; D013534:Survival; D013739:Testosterone / Q000097:blood / Q000172:deficiency / Q000502:physiology; D014481:United States
chemical_list: D013739:Testosterone