Diastolic blood pressure has a J-curve relation with coronary heart disease and death. Because this association is thought to reflect reduced coronary perfusion at low diastolic blood pressure, we hypothesized that the J-curve would be most pronounced in persons with coronary artery calcium. In 6,811 participants from the Multi-Ethnic Study of Atherosclerosis, we used Cox models to examine if diastolic blood pressure category is associated with coronary heart disease events, stroke, and mortality. Analyses were conducted in the sample overall and after stratification by coronary artery calcium score. In multivariable-adjusted analyses, compared with diastolic blood pressure of 80 to 89 mm Hg (reference), persons with diastolic blood pressure <60 mm Hg had increased risk of coronary heart disease events (hazard ratio 1.69 [95% confidence interval 1.02 to 2.79]) and all-cause mortality (hazard ratio 1.48 [95% confidence interval 1.10 to 2.00]), but not stroke. After stratification, associations of diastolic blood pressure <60 mm Hg with events were present only in participants with coronary artery calcium >0. Diastolic blood pressure <60 mm Hg was not associated with events when coronary artery calcium was zero. However, the association between diastolic blood pressure and events did not demonstrate statistical interaction when stratified by presence or absence of coronary calcium. We also found no interaction in the association between low diastolic blood pressure and events based on race. In conclusion, diastolic blood pressure <60 mm Hg was associated with increased risk of coronary heart disease events and all-cause mortality in the sample overall, but this association appeared strongest in individuals with subclinical atherosclerosis.
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