A big rise in pneumonia deaths may be linked to a clampdown on the use of antibiotics for coughs and sore throats, say researchers.
Antibiotics are over-used
University of Aberdeen scientists found pneumonia deaths rose by 50% during a five-year period in the late 1990s.
Doctors were told in 1998 to curb antibiotic use amid concern about growing bacterial resistance.
An expert government advisory panel is now considering whether to revamp its guidance on the use of the drugs.
The Aberdeen study found that excess winter deaths rates - those above average levels - from pneumonia went up from 20.4 per 100,000 in 1995-96 to 30.7 per 100,000 in 1999-2000.
Over the same time period, GPs cut antibiotic prescriptions for lower respiratory tract infections by 30%.
This followed advice from the Specialist Advisory Committee on Antimicrobial Resistance (SACAR) that antibiotics should not be used to treat coughs, colds and sore throats because most are caused by viral infections, which do not respond to antibiotics.
The over-use of antibiotics has been blamed for many bacteria developing resistance to the drugs. This has led to the rise of superbugs such as MRSA.
Researcher Dr Mike Thomas told BBC News Online: "There has been a lot of emphasis to GPs and the general public about the need to resist the use of antibiotics to areas where they are appropriate and effective.
"And we found that during the period of our study there was quite a major fall in antibiotic prescriptions, particularly to people with coughs."
Dr Thomas said further research was required before it could be proved that the rise in death rates from pneumonia was caused by a fall in antibiotic prescriptions.
But he said: "It is quite plausible that it is a significant factor, and it certainly warrants further investigation.
"It is well known that it can be very difficult to diagnose early signs of pneumonia because the symptoms are very similar to those of relatively minor, self-limiting illnesses.
"Even with a careful examination by a GP it can be difficult to pick up early pneumonia. The only way to be sure would be to x-ray everybody who came in with symptoms, and that is not feasible."
However, Dr Thomas stressed the need for caution when dealing with vulnerable people, such as the elderly and those with chronic respiratory problems.
Professor Richard Wise, chair of SACAR, said: "The committee met last week to consider the need to update advice on GP prescribing of antibiotics for lower respiratory tract infections.
"We are concerned that patients might not be receiving optimal treatment for respiratory tract infections but we are cautious about over-interpreting information from one published paper.
"As a result we have asked a number of experts to urgently evaluate the current evidence in detail, and identify further evidence of any potential risk to patients of promoting prudent prescribing.
"Once this is completed, we will be in a position to look at whether changes need to be made to prescribing advice."