Two studies covered in this week's BioNews have caught the attention of the British public. According to press reports, the first study, carried out in Germany, showed a link between the use of disposable nappies on male babies and infertility later in life. The other study, of men and women in the Bristol area, showed that smoking - both passive and actual - affects the time it takes for a woman to conceive.
Both stories received a similar amount of coverage in the media. But given the choice, which one would you choose as the most convincing? The point is, from reading the press reports on the two studies, it's rather difficult to tell. But from a closer reading of the research, a huge discrepancy between the credibility of the two studies emerges.
The German research was carried on 48 baby boys, comparing the difference in the temperature of their testicles when wearing disposable (plastic-lined) nappies and when wearing towelling nappies. The results showed a significant increase in temperature (about one degree Celsius) when the babies were wearing disposables. But whether this increase will have an effect upon the babies' sperm quality or fertility later in life remains to be seen. The authors of the study suggest that plastic-lined nappies may affect male fertility, but they offer nothing more than hypotheses.
Meanwhile, the smoking and fertility study is much more convincing. The research was carried out on a huge sample of people (8,500 couples) over a period of 10 years. It showed that a definite correlation exists between a woman's exposure to cigarette smoke and the length of time it takes her to conceive.
The British study was able to tell us something about the relationship between cigarette smoking and fertility. But the German study was able to tell us very little about the relationship between disposable nappies and fertility. This isn't the fault of the scientists, who in both instances were frank about the conclusions they could draw from their research. But it's typical of what happens when health journalists have neither the time nor, perhaps, the inclination to distinguish between hypothesis and evidence.
The result might be that, since the nappy story broke, a number of parents have switched over to towelling nappies in order to protect their sons' fertility. But it's likely that many of those who have switched were thinking of doing so already. And perhaps, in a few week's time, once the research has been forgotten, the realities of life with re-usable nappies might kick in and normality will be resumed.