When to wait
Researchers from the University of California at Berkeley argue in an article published yesterday in the British Medical Journal recommending the "Parachute approach to evidence based medicine ," that there are times when it is unethical to wait for controlled trials of a health intervention. People die before the intervention is tested, they say, citing as their most impressive evidence the case of Oral Rehydration Therapy (ORT). They explain:
In 1980 childhood diarrhoea was killing an estimated 4.6 million children annually. Treatment with an intravenous drip is life saving but requires health facilities. Studies from 1977 onwards showed that infant diarrhoea could be treated with oral rehydration. The World Health Organization initiated a highly successful programme of oral replacement therapy in 1981 after it became obvious that the treatment saved lives and no alternative home based treatment was possible. Randomised controlled trials were later conducted in health facilities, confirming that oral replacement therapy was as effective as intravenous therapy. The initiation of large scale programmes for oral replacement therapy before the randomised trials meant that by 2000 there were three million fewer deaths from diarrhoea annually.
Treating diarrhea with a mixture of salt, sugar and water has, indeed, saved millions of lives. The authors advocate the "parachute" principle, explaining:
Evidence based medicine and randomised controlled trials are not synonymous. The parachute approach can be the most appropriate, especially in situations of high mortality and low resources, when a simple intervention can have a large impact. Randomised controlled trials are essential in many other settings and they have defined many life saving strategies and corrected some important mistakes. They are often needed when mortality has reached a low level because new treatments require large investment for relatively small improvements in therapy that may be difficult to distinguish.
All that may be well and good, but BMJ has also editorialized that they feel confident in recommending universal sodium reduction. Perhaps a caveat is needed before we call in the airborne assault on salt. In the case of ORT, the small scale studies produced strong consensus of a health benefit. While there is no such concensus that reducing salt would reduce blood pressure to a meaningfull degree, because the effect is so heterogeneous, the UC-Berkeley authors and BMJ editorial staff should be chastened by the consensus of the observational studies of low-salt diets -- there is no benefit in terms of reducing heart attacks or reducing mortality.
Let's not "parachute" in to reduce dietary salt -- at least until the clouds clear and we can see the landing area.
