Possible causes of male fertility decline
So, why is this happening? The short answer: we don’t really know. There are a number of possible hypotheses, but we’ve yet to pinpoint the exact cause for global male fertility decline.
- Lifestyle: exercise, bodyweight, sleep
It won’t surprise most people to hear that, in the Western world, our lives are more sedentary than ever before. A sedentary lifestyle has been shown to be negatively correlated with sperm health. Similarly, about two-thirds of the US and the UK are overweight or obese, a higher number than ever before; excess body weight is linked to lower semen parameters and reproductive hormone levels.
Plus, modern adults aren’t sleeping very well. Today, over 35% of working adults in the US don’t get enough sleep, up from 30% in 2010. Sleeping less than 7–8 hours per night has been correlated with lower markers of male fertility.
However, it’s unlikely to be solely lifestyle factors that fully explain the global decline in sperm count. It turns out that household dogs are also experiencing a significant annual decline in average sperm count, and researchers found high concentrations of certain chemicals in their testes.