Dr Bret Hart

Dr Bret Hart

ED: What do Thomas Edison and Augustinian friar Gregor Johann Mendel have in common? Dr Bret Hart has the answers.

Edison suggested that “The doctor of the future will give no medicine, but will interest his patient in the care of the human frame, in diet and in the cause and prevention of disease.” This might seem fanciful but so were many of Edison’s inventions which became commonplace.

Meanwhile Mendel had sown the (pea) seed of a revolution currently unfolding to untangle causality and correlation. It’s called Mendelian Randomisation (MR) and may help establish that Edison’s prediction is not so farfetched.

MR is akin to a “genetically randomised trial” by exploiting the fact that genotypes are randomly assigned at conception and are, therefore, independent of confounding factors and disease processes.

In the US, the Robert Wood Johnson Foundation explored the correlation between education and longer healthier lives (healthspan). They estimate that college graduates can expect to live five years longer than students who don’t finish school. They also found an additional four years of schooling reduces the risk of diabetes by 1.3%, heart disease by 2.2%, obesity by 5% and smoking by 12% with the benefit crossing generations.

Infant mortality rates (IMR) decrease in proportion to the number of years mothers spend in education. For example mothers with less than 11 years of education have an IMR of 8.1 and mothers with more than 16 years 4.2 per 1000 live births.

The foundation has devised a calculator (countyhealthcalculator.org) to show the impact of altering a State’s level of graduation on rates of diabetes, associated costs and age of death. This dramatically demonstrates outcomes doctors would find hard to emulate.

But all these estimates relate to correlation not causation which would require an unethical trial over several decades to prove. This is where MR is invaluable and was used by Tillman & Vaucher and 15 others across mainly high income countries to clarify the nature of the association between education and coronary heart disease (CHD).

The results published in last year’s BMJ, showed that a genetically determined increase of one standard deviation in length of education (3.6 years) was associated with a clinically important decrease in risk of CHD.

The magnitude of this effect is comparable to the effect of short-term statin use for primary prevention of CHD. But education has many more beneficial side effects than statins can offer.

Teachers focus on the section of the population with the greatest potential for return on investment (ROI) so have greater ability to shift the curve than doctors who respond to demand from those who may be at higher risk of disease but are smaller in number than those at risk in the whole population.

And the demographic shift is feeding a demand for healthcare interventions at the end of life when the ROI is least. The unsustainable health system could take a leaf out of the education system’s learned book.


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