Men may have weaker immune systems than women and suffer disease more seriously and for longer, say scientists at the University of Cambridge, UK. The study, published in the Proceedings of the Royal Society B: Biological Sciences (24 Mar 2010), gives scientific credence to the phenomenon colloquially referred to as 'man flu' and suggests that “Maybe men aren't just playing sick, but really are more susceptible” ( The Times , 24 Mar 2010).

The theoretical study looked at various scenarios to test whether environmental and behavioural factors could have led men and women to evolve slightly different immune systems. The authors propose that the predilection of modern man's ancestors for risky behaviour means they are more exposed to infections but paradoxically this decreases their immunity. “Above a certain level of exposure, the benefit of rapid recovery in males decreases owing to constant reinfection ... this selects for lower resistance in males”, explained the lead author Dr Olivier Restif ( Telegraph , 24 Mar 2010). It was suggested that there could be a trade-off between developing a strong immune system and being reproductively competitive (The Times). Consistent with this hypothesis, testosterone has been shown to interfere with the immune response, potentially putting men with high testosterone levels at greater risk of infection. Indeed, increased susceptibility of males to infections such as malaria has also been reported (The Times).