Low cholesterol increases stroke risk
Part 2: Follow-up studies
A follow-up study by the Institute of Community Medicine, University of Tsukuba, Japan, over a 30-year period confirmed the earlier findings. By that time, heart disease deaths had also fallen by 20%.[1] A later study of both men and women aged 35 to 89 years over the period 1984 to 2001 showed clearly that the really beneficial part of the Japanese diet was their increased intakes of animal fat and cholesterol.[2] In this study, the risk of a stroke was reduced by almost two-thirds (63%) in those who had the highest intake of animal fat and cholesterol, compared to those with the lowest. Animal protein was not significant — just the fat and cholesterol.
These results were not confined to Japan or even to Asia. In 1997, the results of a follow-up of 350,000 men screened for the Multiple Risk Factor Intervention Trial in the United States showed that the excess risk of death from cerebral haemorrhage was 6 times higher in middle-aged men with low blood cholesterol levels.[3]
Scientists at the Cardiovascular Health Research Unit, Washington University, conducted an analysis of 13 randomised controlled trials to look at the effects of lowering blood cholesterol on diseases other than CHD.[4] They found that while lowering cholesterol resulted in a slight lowering of non-fatal strokes, fatal strokes were increased by 32%, and where cholesterol was lowered by a drug, the death rate from stroke rose by a huge 264%.
Because strokes and cerebral haemorrhages are rare in younger people, there has been little research done at these lower ages. However, cerebral haemorrhages are now affecting people younger than 40. Doctors at the Stroke Clinic, Instituto Nacional de Neurologia y Neurocirugia, Mexico City, looked into this new phenomenon.[5] They found a number of 'risk factors' including smoking, drinking alcohol and raised blood pressure. You might expect that high blood pressure posed the most risk, but that only accounted for 13%. The highest risk, at 35%, was low blood cholesterol levels.
The connection between low cholesterol levels and haemorrhagic stroke cannot be dismissed.
References
1. Iso H, Shimamoto T, Kitamura A, Iida M, Komachi Y. Trends of cardiovascular risk factors and diseases in Japan: implications for primordial prevention. Prev Med 1999; 29: S102-5.2. Sauvaget C, Nagano J, Hayashi M, Yamada M. Animal Protein, Animal Fat, and Cholesterol Intakes and Risk of Cerebral Infarction Mortality in the Adult Health Study. Stroke 2004; 35: 1351.
3. Gillman MW, et al. Inverse association of dietary fat with development of ischemic stroke in men. JAMA 1997; 278: 2145-50.
4. Atkins D, Psaty BM, Koepsell TD, et al. Cholesterol reduction and the risk of stroke in men. A meta-analysis of randomized, controlled trials. Ann Int Med 1993; 119: 136-45
5. Ruiz-Sandoval JL, Cantu C, Barinagarrementeria F. Intracerebral hemorrhage in young people: analysis of risk factors, location, causes, and prognosis. Stroke 1999; 30: 537-41.
