The problem with scientific research about bed sharing
09-03-2015
There is a huge amount of contention regarding whether parents should sleep in the same bed as their newborns. On one side of the argument are those who believe that it creates a risk of smothering and sleep problems while on the other side are those who think that it not only helps parents to bond with their children but also makes the nightly wake and feed ritual that much easier for all involved. This is a problematic area, but it is one that needs to be discussed as it is an issue that all parents face. We offer this new research with the proviso that this is an area that parents need to research themselves thoroughly so they can make an informed decision. In fact, this study will show you why you need to read widely as there are some major flaws with it. Please use this information as a warning that you should never take a single piece of research as gospel but should rather read widely and then come to your own decision.
Right, with the somewhat onerous warning and caveat out of the way, let us have a look at this new research, which is focused on sleep problems through bed sharing. A study in the Journal of Developmental and Behavioral Pediatrics, which is ranked 13th out of the 100 journals in the field which makes it highly respect, has recently caused renewed debate about the risks of bed sharing with your infant. However, while the study claims that sharing a bed actually harms infant sleep at 18 months by doubling the risk of “sleep problems” many think that there are issues with the study.
How did they do the study?
Ok, so let us look at the study. The information was gathered as an aspect of the Norwegian Mother and Child Cohort Study, which follows a number of families every six months throughout their lives to monitor a wide variety of different issues. The data is collected using questionnaires and the overall study is viewed by all as a useful and valid project. For the research in question, data from birth, six months and 18 months was used. In total there were 55,831 children used in this project ( as the project used data that the Norwegian Mother and Child Cohort Study had gathered from 1999 to 2008). The results have been controlled for all the key metrics, including maternal age, birth weight, infant sex, gestation, and parity while the sleep variables were categorical, which means parents did not provide absolute times but rather general times. The categories for nightly sleep were set at less than 10 hours, 11-12 hours, 13-14 hours, and more than 15 hours. The categories for night waking were 3 or more times each night, 1-2 times ever night, 1-2 times a week and seldom or never. The bedsharing component was examined by asking the parents “Does your child sleep (at least half the night) in the same bed as their mother/father?” The respondents were given the options of ‘often’, ‘sometimes’ and ‘no’.
What were they looking for?
The researchers then defined having a sleep problem as being less than 12 hours of sleep each night or still having nightly waking when they were 18 months of age. This is where many have an issue with the study. This definition of a sleep problem is not a common one, nor is it consistent with what other experts may consider a ‘problem’. In fact, there is no evidence that this is even problematic at all. What is particularly interesting is that the questionnaire asks parents if they thought that their child had a sleep problem and far less thought so than the findings of the research would indicate. While only 2.5% of families reported that they thought their child had a sleep problem the research found that there was a whopping 26 per cent and 38 per cent as defined by their criteria of less than 12 hours and still waking at 18 months respectively.
Why did they call these factors ‘problematic’?
So why would they use these cut off points to decide whether bed sharing was problematic or not? Well the less than 12 hours of sleep indicator came because the median amount of sleep for the cohort was 13-14 hours but as anyone with a decent background in statistics knows you do not need to be in the median to be considered ‘normal’ and in fact using proper statistical analysis of the overall data from the Norwegian Mother and Child Cohort Study shows that a very small number of children fall into the abnormal range (as defined by being statistically anomalous). Interestingly that number is virtually the same as the 2.5 per cent of parents who believed that their children had a sleep problem. What they decide to call a sleep problem are the large group of children who simply fall below the median, not just ignoring good statistical principles but also common sense.
Similarly with the nightly wakings issue, the researchers have arbitrarily decided that waking at night at all when a child is 18 months is problematic and yet have not looked at other vital factors that may influence this such as whether the child is still being breastfeed. A child who is being breastfed is more likely to wake at night and they may simply be the children who are also more likely to be in their parents’ bed than a child who is not. The problem is that the study doesn’t look into this, but rather presents the findings as solid when really there are a number of conceptual and design issues that mean it is flawed.
However, while this study may be ‘problematic’ this doesn’t mean you should ignore the wider body of research on this area as on the whole the findings are useful. What it should tell you is that you should always do your own research and you should always come to your own conclusions. Never simply take one study as fact.
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