Friday June 20 2008
In the study, 216 children used a dummy
“Dummy use link to ear infections,” is the headline on BBC News today. The report quotes a five-year study of almost 500 Dutch children, which suggests that “parents should avoid using a dummy in infants who are prone to ear infections”.
The story is based on a study which showed that the risk of recurrent ear infections was almost double in infants who used a dummy (pacifier) compared with those who didn’t. However, the design of the study means it is not possible to conclude that dummy use causes or increases the risk of recurrent ear infections. Recurrent ear infections are painful, and this could lead to an increased use of dummies. It is not clear if parents had a tendency to use dummies in children who were prone to recurrent ear infections, because of their pain.
At present, parents who use dummies or pacifiers to calm their baby should not be overly concerned by these research findings. Infections are extremely common in young children and have many causes. Being alert to the common signs of infection – increases in temperature and distress level – will allow parents to begin appropriate pain relief, such as paracetamol, early.
Where did the story come from?
Dr Maroeska Rovers and colleagues from the University Medical Center Utrecht in the Netherlands carried out this research. No funding was declared for this study, which was approved by the ethical committee of the university. It was published in the peer-reviewed medical journal Family Practice.
What kind of scientific study was this?
This was an analysis of data collected as part of an ongoing cohort study – the Utrecht Health Project – which recruits participants continuously in the new residential area of Utrecht in the Netherlands. All new inhabitants are invited to participate in the study when they register with a GP in the area. Those who agree fill in questionnaires about their health history. The GPs record all medical diagnoses and treatment, and these are coded.
The researchers examined these computer records to find all codes relating to ear infection (acute otitis media) and recurrent ear infections. Recurrent ear infection was defined as three or more doctor-diagnosed episodes of ear infection during the study period. Four hundred and ninety-five children between birth and four years old were included in the study. These were all the children recruited between 2000 and 2005. Of these, nineteen children had birth defects and were excluded; this left 476 children for review.
At the start of the study, the parents of these children filled out a questionnaire about their child’s health, including the use of dummies. Other factors that the researchers thought might influence the results were collected from the notes. This included basic information on day care attendance, breastfeeding, passive smoking, use of a feeding bottle, thumb sucking, educational level of the parents, atopy/allergies and ethnicity. Information on coughs and colds was also obtained from the codes in the electronic medical files. The researchers then used statistical methods to look at the association between dummy use and ear infection or recurrent ear infection, taking these factors into account.
What were the results of the study?
Among the 216 children identified by their parents in the first questionnaire as using a dummy, 76 (35%) developed at least one ear infection. Of the 260 children that did not use a dummy, 82 (32%) developed at least one ear infection. For recurrent ear infections, these figures were 33 (16%) versus 27 (11%) respectively.
The researchers quote the adjusted odds ratios for pacifier use and ear infections and recurrent ear infections to show that the difference was not statistically significant for single episodes, but was significant for recurrent episodes. These were 1.3 (95% CI 0.9–1.9) and 1.9 (95% CI 1.1–3.2) respectively.
What interpretations did the researchers draw from these results?
The researchers conclude that “pacifier use appears to be a risk factor for recurrent acute otitis media”, and they go on to suggest that parents should be informed about the possible negative effects of using a dummy once their child has been diagnosed with an ear infection, in order to avoid recurrent episodes.
What does the NHS Knowledge Service make of this study?
The researchers have shown an association between dummy use and the risk of recurrent ear infections. However, from this type of study it is not possible to say that one causes the other.
- In this prospective study, the questionnaires about dummy use were handed out before any ear infections developed. This has reduced some of the potential problems that could occur if questionnaires had been handed out after the ear infections occurred, as “recall bias” can lead to misleading results.
There are some other issues which limit the conclusions that can be drawn from this research:
- It is not possible to determine accurately how often and for what length of time the dummy is used. Information about dummy use was obtained by questionnaire at one time point only, and was quantified as “sometimes” or ”often”. These definitions mean a wide range of dummy use was included in each category, from a few months as a baby, to those who used them continuously on a daily basis for up to several years. Assessment at one time point cannot give a clear indication of dummy use throughout the whole of infancy. It is not possible to tell from the study whether questions were targeted towards frequency of dummy use within the past day, past week (which may not represent use at other times) or an estimate of use throughout infancy. These differences may cause some error in the quantification of dummy use.
- The time relationship between the use of a dummy and the development of ear infections is not clear, as dummy use was only recorded once. Dummy use was assessed at the start of the study, and ear infections were assessed in all follow-up thereafter. Therefore, a child could have used a dummy occasionally as a baby and then stopped before developing recurrent ear infections as a child. This means it cannot be concluded that a child using a dummy is at risk of developing an ear infection.
- The study is only able to identify ear infections that required a GP visit. Ear infections are very common in infants and young children, and many parents will allow the infection to resolve itself without seeking medical advice. Therefore, the actual incidence of ear infections among the study group may have been greater than that recorded.
- The only way to determine accurately whether a dummy causes recurrent ear infection would be to carry out a randomised controlled trial, with some infants using dummies and some not, and then seeing whether there was a difference in the rate of ear infections between the groups.
At the current time, parents who use dummies to calm their infant should not be overly concerned by the research findings. Infections are extremely common in young children, and they have many causes. Being alert to the common signs of infection – increases in temperature and distress level – will allow parents to begin appropriate pain relief, such as paracetamol, early.