title: The associations of age, lifestyle factors and chronic disease with testosterone in men: the Tromsø Study.
abstract: OBJECTIVE
  To study whether lifestyle factors and/or chronic disease are associated with the age-related decline of total and free testosterone in men, or if these factors might be associated with the variation of total and free testosterone but not with their age-related decline.
  
  
  METHODS
  A population-based, cross-sectional study was used.
  
  
  METHODS
  Total testosterone and sex hormone binding globulin (SHBG) levels were analyzed and free testosterone levels were calculated in 1563 men participating in the Tromsø study in 1994/1995. Anthropometric characteristics were also measured and two standardized questionnaires completed, including lifestyle factors and medical history. The data were analyzed with multiple linear regression analysis of covariance, and logistic regression.
  
  
  RESULTS
  Total and free testosterone were inversely associated (P=0.001 and P<0.001), while SHBG was positively associated (P<0.001) with age. Body mass index (BMI) was inversely associated with total (P<0.001) and free (P=0.016) testosterone and SHBG (P<0.001). Both total and free testosterone were positively associated with tobacco consumption (P<0.001 and P=0.004) and total testosterone was positively associated with coffee consumption (P<0.001). SHBG was positively associated with smoking (P=0.004) and coffee consumption (P<0.001). Men who reported having had a stroke or having a cancer diagnosis had lower levels of total testosterone (P<0.001 and P<0.01) and free testosterone (P<0.01).
  
  
  CONCLUSIONS
  BMI and smoking are independent contributors to the variation of total and free testosterone and SHBG levels, and coffee consumption to the variation of total testosterone and SHBG. Thus, lifestyle factors can have a direct effect on circulating levels of free endogenous sex hormones and to total levels due to the effect on SHBG levels.
authors.affiliation: Department of Medicine, University Hospital of North Norway, N-9038, Tromsø, Norway. johan.svartberg@unn.no
authors.forename: Johan
authors.initials: J
authors.lastname: Svartberg
authors.forename: Monica
authors.initials: M
authors.lastname: Midtby
authors.forename: Kaare H
authors.initials: KH
authors.lastname: Bønaa
authors.forename: Johan
authors.initials: J
authors.lastname: Sundsfjord
authors.forename: Ragnar M
authors.initials: RM
authors.lastname: Joakimsen
authors.forename: Rolf
authors.initials: R
authors.lastname: Jorde
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D000465:Algorithms; D001827:Body Height / Q000502:physiology; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D002908:Chronic Disease; D003069:Coffee; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008019:Life Style; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009664:Norway; D011153:Population; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D012907:Smoking / Q000097:blood; D011795:Surveys and Questionnaires; D013739:Testosterone / Q000097:blood*
chemical_list: D003069:Coffee; D012738:Sex Hormone-Binding Globulin; D013739:Testosterone