“There have been previous studies investigating the association of paternal smoking with semen quality, but these were small studies without information on key confounders,’ said Dr Tøttenborg from Bispebjerg Frederiksberg Hospital, in Copenhagen, Denmark. ‘Our larger study does support these previous findings that paternal smoking is associated with sperm concentrations in male offspring independently of maternal smoking.”
The study was a follow-up analysis of 778 19-year-old young men born to mothers registered in the Danish National Birth Cohort between 1996 and 2002. Results showed that in the adjusted analyses the sons of fathers who smoked daily (and where the mothers did not smoke) had an 8% lower sperm concentration and 9% lower total sperm count than the sons of paternal non-smokers.
“Our results did show an association with paternal smoking,’ said Dr Tøttenborg, ‘but the effect of maternal smoking is much larger. If the mother but not the father smoked, the reduction was 26% for sperm concentration and 46% for sperm count. It’s certainly worse for the boys if the mother smokes. Nevertheless, the circumstances in which the father smokes but the mother doesn’t is much more prevalent, so this is still very relevant for public health. A decline in sperm count of 8-9% can seriously affect the fertility of men with already sub-optimal sperm quality.”
The likely explanation for a preconceptional or prenatal effect of paternal smoking in the offspring is epigenetic, by which paternal smoking can induce alterations in the sperm genome which in turn may be transmitted to the cells of the offspring.
Following her presentation Dr Tøttenborg was interviewed live on ESHRE’s online channel and the news was amongst others featured by The Daily Mail. You can read the full press release and listen to the interview here.