title: No association between body mass index and sperm DNA integrity.
abstract: OBJECTIVE
  Is overweight associated with impaired sperm DNA integrity?
  
  
  CONCLUSIONS
  High body mass index (BMI) is not associated with impaired sperm DNA integrity as assessed by the DNA Fragmentation Index (DFI).
  
  
  BACKGROUND
  Previous studies, based on fewer subjects and including mainly subfertile men, have shown conflicting results regarding the influence of overweight and obesity on sperm DNA integrity.
  
  
  METHODS
  This cross-sectional study was based on semen samples from 1503 men from the general population.
  
  
  METHODS
  We included two cohorts (cohort A and B) of military recruits (n = 275, n = 304, respectively), one group (cohort C) of fertile men and men without known fertility problems (n = 724), and one group (cohort D) of men between 19 and 40 years without known fertility problems (n = 200). In all cohorts, data were available on BMI, DFI as measured by the sperm chromatin structure assay (SCSA), standard semen characteristics, and potential confounders (age, abstinence time, smoking habits). The subjects were categorized according to BMI into four groups: underweight (<18.5 kg/m(2)), normal weight (18.5-24.9 kg/m(2)), overweight (25.0-29.9 kg/m(2)) and obese (≥30.0 kg/m(2)). Using a linear regression model, the inter-group differences in DFI were calculated. Furthermore with the normal-weight group as the reference, the odds ratios (ORs) for DFI > 20% and DFI > 30%, were calculated for the other groups. Calculations were made for the material as a whole and after exclusion of cohort C which included proven fertile men.
  
  
  RESULTS
  We found that normal-weight men had significantly higher DFI than overweight men, with a mean difference of 1.13% (95% CI: 1.05-1.22%); P = 0.001). Overweight men had a reduced risk of having DFI ≥ 20% and DFI ≥ 30%, compared with normal-weight men; adjusted odds ratio (OR) = 0.61 (95% CI: 0.42-0.88; P < 0.01) and adjusted OR = 0.48 (95% CI: 0.28-0.84; P < 0.01), respectively. When excluding cohort C, the statistical significance was lost. Regarding standard semen parameters, we found that obese men had a higher percentage of progressive motile spermatozoa than normal-weight men; mean difference 1.15% (95% CI: 1.02-1.30%, P < 0.05) but the significance was lost when excluding cohort C. All other standard semen parameters were unaffected by BMI.
  
  
  CONCLUSIONS
  A main limitation might be the cross-sectional nature of the data. Furthermore our study included a significant proportion of men with proven fertility (75% of cohort C, n = 550), and could therefore be biased toward fertility.
  
  
  CONCLUSIONS
  Our study indicates that overweight per se is not associated with a higher level of sperm DNA damage.
  
  
  BACKGROUND
  This research has been given grants from the following: EU 5th and 7th framework program (Inuendo and Clear projects, [Contracts no. QLK4-CT-2001-00202 and FP7-ENV-2008-1-226217)]), the Swedish Research Council (Grants No. 2007-2590, 521-2004-6072 and 521-2002-3907); the Swedish Governmental Funding for Clinical Research, Skåne county council's research and development foundation, MAS Funds, University Hospital MAS Foundation in Malmö, Crafoordska Fund, Ove Tulefjords Fund, Foundation for Urological Research, Fundacion Federico SA, and Gunnar Nilssons Cancer Fund. The authors declare that there are no conflicts of interest.
authors.affiliation: Reproductive Medicine Centre, Skåne University Hospital, SE 205 02 Malmö, Sweden Department of Translational Medicine, Malmö, Lund University, SE 205 02 Malmö, Sweden ida.bandel@med.lu.se aleksander.giwercmanl@med.lu.se.
authors.forename: I
authors.initials: I
authors.lastname: Bandel
authors.affiliation: Reproductive Medicine Centre, Skåne University Hospital, SE 205 02 Malmö, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Bungum
authors.affiliation: Department of Translational Medicine, Malmö, Lund University, SE 205 02 Malmö, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Richtoff
authors.affiliation: Department of Laboratory Medicine Malmö, Section for Clinical Chemistry, Lund University, SE 205 02 Malmö, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Malm
authors.affiliation: Reproductive Medicine Centre, Skåne University Hospital, SE 205 02 Malmö, Sweden Department of Translational Medicine, Malmö, Lund University, SE 205 02 Malmö, Sweden Occupational and Environmental Medicine, Skåne University Hospital, SE 221 85 Lund, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Axelsson
authors.affiliation: University of Greenland, 3900 Nuuk, Greenland, Denmark.
authors.forename: H S
authors.initials: HS
authors.lastname: Pedersen
authors.affiliation: Department of Toxicology and Risk Assessment, National Institute of Public Health - National Institute of Hygiene, Warsaw, Poland.
authors.forename: J K
authors.initials: JK
authors.lastname: Ludwicki
authors.affiliation: Department of Toxicology and Risk Assessment, National Institute of Public Health - National Institute of Hygiene, Warsaw, Poland.
authors.forename: K
authors.initials: K
authors.lastname: Czaja
authors.affiliation: Department of Toxicology and Risk Assessment, National Institute of Public Health - National Institute of Hygiene, Warsaw, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Hernik
authors.affiliation: Department of Occupational Medicine, Aarhus University Hospital, DK-8000 Aarhus C, Denmark Department of Clinical Epidemiology, Aarhus University Hospital, DK-8200 Aarhus N, Denmark.
authors.forename: G
authors.initials: G
authors.lastname: Toft
authors.affiliation: Department of Environmental and Occupational Medicine, Copenhagen University Hospital, 2400 Copenhagen, Denmark.
authors.forename: J P
authors.initials: JP
authors.lastname: Bonde
authors.affiliation: Laboratory of Toxicology, Unit of Radiation Biology and Human Health, BIORAD-TOSS, ENEA Casaccia Research Centre, 00123 Rome, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Spanò
authors.affiliation: Department of Translational Medicine, Malmö, Lund University, SE 205 02 Malmö, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Malm
authors.affiliation: Faculty of Health Sciences, Oslo and Akershus University College of Applied Sciences, N-0130 Oslo, Norway.
authors.forename: T B
authors.initials: TB
authors.lastname: Haugen
authors.affiliation: Reproductive Medicine Centre, Skåne University Hospital, SE 205 02 Malmö, Sweden Department of Translational Medicine, Malmö, Lund University, SE 205 02 Malmö, Sweden ida.bandel@med.lu.se aleksander.giwercmanl@med.lu.se.
authors.forename: A
authors.initials: A
authors.lastname: Giwercman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015992:Body Mass Index; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D053938:DNA Fragmentation; D005062:European Union; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology; D050177:Overweight / Q000453:epidemiology; D012042:Registries; D055101:Semen Analysis; D013094:Spermatozoa; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
keywords: DNA fragmentation index; body mass index; male infertility; semen quality