title: [Association between age and quality of semen in Chinese males with normal fertility].
abstract: OBJECTIVE
  To explore the association between age and variables of semen in Chinese males with normal fertility.
  
  
  METHODS
  The population size under study would consist of 946 fertile male volunteers from 6 provinces of China, aged between 20 and 59. Semen quality was analyzed by hand on site and background information was obtained through structured questionnaire. Trend chi-square test and multiple linear regression methods were used and 95%CI were calculated to serve as reference value of semen variables of different age group.
  
  
  RESULTS
  The normal percent of motility and living sperm declined significantly while the ascending of age, they were 55.7% and 97.3% in age < 30 group when compared to 21.9% and 90.3% in the age 50 - 59 group respectively. Under control of confounding factors as for center and abstinence time, all semen variables except semen volume were significantly different among the age groups. Sperm concentration, percentage of sperm motility and normal morphology sperm decreased significantly after age 40 while percentage of living sperm decreased after age 50 - 59 group. Sperm concentration among the 50 - 59 year-old group appeared to be lower than the 40 - year-old group.
  
  
  CONCLUSIONS
  The influence of age must be taken into account when evaluating the quality of semen.
authors.affiliation: Population and Family Planning Commission of Shanghai, Shanghai 200003, China.
authors.forename: Yuan-qi
authors.initials: YQ
authors.lastname: Cui
authors.forename: Er-sheng
authors.initials: ES
authors.lastname: Gao
authors.forename: Wei-jin
authors.initials: WJ
authors.lastname: Zhou
authors.forename: Jun-qing
authors.initials: JQ
authors.lastname: Wu
authors.forename: Wei
authors.initials: W
authors.lastname: Yuan
mesh_terms: D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D016009:Chi-Square Distribution; D002681:China; D005298:Fertility; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012661:Semen / Q000166:cytology / Q000502:physiology*; D013076:Sperm Count / Q000706:statistics & numerical data; D013081:Sperm Motility / Q000502:physiology; D011795:Surveys and Questionnaires; D055815:Young Adult