How low should blood pressure be? Heart and Vessels.

A low diastolic blood pressure (DBP) has been associated with an increased risk of coronary events in the elderly subjects and those with a history of cardiovascular disease. As this may reflect impaired coronary flow in subjects in which BP is lowered too much, implications for treatment have been contemplated. Recently, however, it was proposed that a low DBP could result from stiffening of arteries and be a consequence of atherosclerosis. This could explain increased risk and suggests that discontinuation of treatment in patients with a low diastolic and a high systolic BP may not be warranted. We examined low DBP and atherosclerosis in the Rotterdam Study, a population based cohort study among 7983 men and women aged 55 years and over. The degree of atherosclerosis was estimated using ultrasonographic measurements of intima-media thickness of the carotid artery. A significant J-shaped association was present between carotid artery wall thickness and DBP with a nadir at 60-69 mmHg. Subsequently, the relation between progression atherosclerosis of the abdominal aorta and change in DBP was investigated in a longitudinal study among 510 women, initially aged 45 to 64 years followed over a nine year period. Aortic atherosclerosis was graded based on calcified deposits on abdominal X-rays. The age adjusted relative risk of atherosclerosis progression in women with a decrease in DBP of 10mmHg or more was 2.5 (95% CI 1.3-5.6) compared to a smaller decrease or increase. Our findings suggest that progression atherosclerosis maay lead to a fall in DBP. Low DBP in certain subjects may be a consequence of atherosclerois rather than a cause of the increased risk