For the last half century, heart disease has been the most common cause of death in rich countries — more common than cancer, for example. I recently discussed the observation of David Grimes, a British gastroenterologist, that heart disease has followed an infectious-disease epidemic-like pattern: sharp rise, sharp fall. From 1920 to 1970, heart disease in England increased by a factor of maybe 100; from a very low level to 500 deaths per 100,000 people per year. From 1970 to 2010, it has decreased by a factor of 10. This pattern cannot be explained by any popular idea about heart disease. For example, dietary or exercise or activity changes cannot explain it. They haven’t changed the right way (way up, way down) at the right time (peaking in 1970). In spite of this ignorance, I have never heard a health expert express doubt about what causes heart disease. This fits with what I learned when I studied myself. What I learned had little correlation with what experts said.
Before the epidemic paper, Grimes wrote a book about heart disease. It stressed the importance of latitude: heart disease is more common at more extreme latitudes. For example, it is more common in Scotland than the south of England. The same correlation can be seen in many data sets and with other diseases, including influenza, variant Creuztfeldt-Jacob disease, multiple sclerosis, Crohn’s disease and other digestive diseases. More extreme latitudes get less sun. Grimes took the importance of latitude to suggest the importance of Vitamin D. Better sleep with more sun is another possible explanation.
The amount of sunlight has changed very little over the last hundred years so it cannot explain the epidemic-like rise and fall of heart disease. I asked Grimes how he reconciled the two sets of findings. He replied:
It took twenty years for me to realize the importance of the sun. I always felt that diet was grossly exaggerated and that victim-blaming was politically and medically convenient – disease was due to the sufferers and it was really up to them to correct their delinquent life-styles. I was brought up and work in the north-west of England, close to Manchester. The population has the shortest life-expectancy in England, Scotland and Northern Ireland even worse. It must be a climate effect. And so on to sunlight. So many parallels from a variety of diseases.
When I wrote my book I was aware of the unexplained decline of CHD deaths and I suggested that the UK Clean Air Act of 1953 might have been the turning point, the effect being after 1970. Cleaning of the air did increase sun exposure but the decline of CHD deaths since 1970 has been so great that there must be more to it than clean air and more sun. At that time I was unaware of the rise of CHD deaths after 1924 and so I was unaware of the obvious epidemic. I now realize that CHD must have been due to an environmental factor, probably biological, and unidentified micro-organism. This is the cause, but the sun, through immune-enhancement, controls the distribution, geographical, social and ethnic. The same applies to many cancers, multiple sclerosis, Crohn’s disease (my main area of clinical activity), and several others. I think this reconciles the sun and a biological epidemic.