Children are now developing ear infections (also known as Otitis Media - OM) towards Christmas time, about two months later than in past decades. Analysis of trends over the years from the General Practice Research Database suggests a link to global warming - and researchers are warning that GPs could be put under relatively more pressure in treating the condition in what is already one of the busiest periods of the year for health workers.

Deafness Research UK has funded two scientists to investigate trends in this common disease, using a large database of GP consultations from the 2000s. These and figures from other countries had shown consultations for OM gradually declining over the years. But when taking  the annual winter maximum into account, the researchers had not expected  to find it displaced; the usual sharp October rise was now coming much later in the autumn months, with the  decline being steepest for the autumn months. A possible explanation is down to the warmer autumns in recent years preventing the seasonal viruses, which cause colds and trigger OM, from getting established. If this is indeed the major factor involved, then some further evidence for consequences of climate change is coming from a rather unexpected source.

A major consequence of OM is glue ear - the retention of fluid in the middle ear for some weeks after an ear infection - and causing hearing loss and problems with communication and behaviour. Its annual cycle is a month or more delayed from the cycle for OM. The researchers found the glue ear peak also to be occurring later in recent years, just like the cycle for the primary infection.

"It is known that overall global warming  has been slower recently, but the autumn rise in ear infection consultations in the UK has still been happening later and later," said Professor Mark Haggard, Deafness Research UK Chairman and Senior Visiting Researcher at the University of Cambridge.

"We have controlled for as many of the known factors as possible and we find a close link to the actual month-to-month temperatures within the years studied. So we have to consider that the overall change in pattern also is partly due to changing aspects of climate, particularly the milder autumns of recent years. Some of the respiratory viruses are temperature-sensitive. "

Professor Haggard has been analysing the data with fellow Deafness Research UK advisor Dr. Ian Williamson of the Department of General Practice at Southampton University who, as a practicing GP, has a strong interest in the implications of the data for UK GPs. "The timing and nature of advice to GPs and parents may have to reflect these changing patterns," added Dr Williamson. "In those children who do get glue ear following an ear infection, more of this will be occurring in December rather than November. This is a period when there are other pressures on families and some scaling-down of non-emergency health services. Nevertheless it is still necessary to look out for children who miss sounds and appear not to be paying attention, or are being less cooperative than usual, as these are the signs of glue ear."

A difficult condition for doctors to diagnose, glue ear is even more challenging for parents and teachers who are those usually most likely to encounter and observe the early signs. Many cases clear up on their own, but if the hearing loss is definite and left untreated, glue ear can lead to behavioural and educational problems. For some cases, grommets are an effective treatment: they are very small tube-like devices  surgically inserted into the eardrum, enabling ventilation of the middle ear aiding natural clearing of the fluid and discouraging the return of the infection. Attitudes and approaches to both ear infections and glue ear have changed over the years. But this seems not to explain the findings from the latest analyses.

"There can be many things changing with time in a  set of data like this," says Prof Haggard. "However, the change in clinical and public attitude to the necessity for antibiotics in otitis media has mostly bottomed out having started in the decade before. Any minor further NHS changes of a financial or administrative nature cannot on their own explain the divergence between seasons over the last decade."

Vivienne Michael, Chief Executive of Deafness Research UK, said: "Glue ear remains a problem among young children and this latest research could prove useful in helping GPs and others in the health service to recognise where the peaks and troughs are now likely to be so they can provide the necessary cover."

For further information on deafness and deafness-related conditions call freephone 0808 808 2222 or visit Deafness Research UK's website at www.deafnessresearch.org.uk