Worth a thousand words…

Cochrane collaboration name and logo

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The Cochrane collaboration is named after Archie Cochrane (pictured above) who died in 1988. He was very influential in developing evidence-based medicine, believing that the limited medical resources should be directed to those forms of health care which were of proven efficacy. In 1979 he suggested awards for the most and least scientifically based specialties – and awarded last place to obstetrics. Obstetricians took up the challenge and, led by Sir Iain Chalmers and colleagues, set up and developed the Oxford Database of Perinatal Trials in the 1980s, the forerunner of the Cochrane Database of Systematic Reviews.

The logo shows a review of data from the first randomised trials of antenatal corticosteroids to prevent neonatal respiratory distress syndrome. In 1988 the lack of a systematic review meant that most obstetricians did not realise that the treatment was so effective. As a result, tens of thousands of premature babies died unnecessarily. The most recent version of this graph is shown on the right. (images courtesy of The Cochrane collaboration.)

The ‘Hawthorne effect’

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The Hawthorne effect is said to occur when people improve an aspect of their behaviour in response to the fact that they are being studied. This is commonly seen in observational studies and can cause the researcher to believe that it is the intervention that is improving the outcome, whereas it would have improved even with a placebo. A randomised trial neutralises this effect because its control group provides a baseline that includes the ‘Hawthorne effect’. Any additional benefit of the intervention can then be attributed to the intervention alone.

This effect was first described at the Hawthorne Works (above), a large factory outside Chicago that produced telephones. In the 1920s the managers wanted to see whether the light levels affected workers’ productivity. But the productivity improved whatever changes were made, even when light levels went back to normal. The researchers concluded that the effect occurred as a result of the interest being shown in them. (photograph courtesy of Hawthorne works museum.)