A 10-year study by Danish scientists found that breast cancer screening programmes produced just a 1% drop in the death rate in some areas, particularly where women between the ages of 55 and 74 were concerned.
In those too young to benefit from screening, namely the 35-54 age group, breast cancer death rates fell by 5% per year in the screened areas and 6% per year in the non-screened areas.
For older age groups (75 to 84), there was little change.
The researchers said that the programmes had created a culture of “overdiagnosis” in which some women underwent treatment for cancers that were highly unlikely to kill them.
An investigation by the same team last year found that one in three breast cancers detected were harmless.
The latest study, based on data generated in the UK, Canada, Australia, Sweden and Norway, was published in the online version of the British Medical Journal.