A comprehensive review on the role of cholesterol in health and a critique of the use of statins has recently been published by a team of Japanese researchers (1). This pulls together information from a range of different sources. The focus is on all-cause mortality because fundamentally that is the key parameter most people understand and wish to control. Determination of individual diseases are subject to bias and lack of objectivity, which does not apply to death. The relationship between all-cause mortality and the cholesterol in the blood has now been investigated repeatedly in many different countries and the results which are incredibly consistent may come as a surprise to many people. In this blog I will refer to a selection of what is available.
Japan
In the Ibaraki Prefecture Health Study, 91,219 men and women aged 40-79 years without any history of stroke or coronary heart disease (CHD) were followed for just over 10 years. It was found that the all-cause mortality was inversely correlated with the level of LDL cholesterol. In other words the higher the LDL cholesterol the greater the life expectancy, which of course is in direct conflict with the conventional wisdom.
In the Isehara Study, data was collected from those who had an annual check-up. The final database contained information on 8,340 men (aged 64±10 years) and 13,591 women (61±12 years). Again it was found that the level of LDL cholesterol was inversely related to the all-cause mortality rate. Interestingly it was reported that, the mortality rates due to cancer in men and to respiratory disease without cancer (mostly pneumonia) in men and women were lowest in those groups with the highest values.
The Jichi Medical School Cohort Study is one of the most recent, large epidemiological studies conducted in Japan in which 12,234 healthy adults from rural communities were followed for almost 12 years. Once again, the highest death rates from all causes was in those with the lowest TC values. In this investigation even the exclusion of deaths within the first 5 years did not alter the relationship between low TC levels and the high mortality. The exclusion of deaths caused by liver disease also made no difference to this conclusion. However in this study the relationship between the death rates and TC levels in men was U-shaped so there was some increase at the higher values. But in women it was clear that as the higher the TC, the lower the death rate.
Norway
The results of the Jichi Study are very similar to those obtained in the HUNT Study conducted in Norway, in which 52,087 men and women aged 20-74 years were followed over a 10-year period (2). TC levels were measured and details of any deaths which occurred were recorded. The results are shown in Table 1.
For both men and women, the highest all-cause mortality was in those with the TC levels below 5.0 mmol/L.
In men, there was no increase in the all-cause mortality with raised TC. Those with a TC level between 5.0 and 5.9 mmol/L had the lowest death rate, which was 23% lower than those with a TC below 5.0 mmol/L. At higher values, the rate increased again.
For women the pattern is different. The higher the TC, the lower the risk of dying from all causes. Compared with those with a TC below 5.0 mmol/L, those with the highest TC levels were 28% less likely to die from all cause
No comments:
Post a Comment