Long-term changes of blood pressure before cardiovascular mortality: A nested case-control study

Abstract

Background : Although many epidemiologic studies have assessed the association between changes of the blood pressure and cardiovascular disease (CVD), any information on the long-term blood pressure change before cardiovascular mortality, with performing repeated blood pressure measurements, is limited in Korea. The aim of this study was to investigate the association between the long-term changes of the blood pressure and the cardiovascular mortality of Korean adults.

Methods : We performed a nested case-control study in the Korea Medical Insurance Corporation Study cohort. From 1990, we measured the blood pressure and major CVD risk factors every two years in 108,461 men and 64,119 women who were aged from 35 to 59 years. The causes and dates of death were obtained from the National Statistical Office of Korea. The cases consisted of 1,636 people who died from CVD between 1993 and 2004 and the controls were 3,272 survivors at the time of sampling. We sampled two controls per case using incidence-density sampling and matching for gender and age.

Results : The people who died from CVD had higher blood pressure than did their controls. These differences were statistically significant from 14 years before death (p<0.001 for all examinations). During the 14 years, the systolic blood pressure significantly increased in the people who died from CVD (p<0.001) but not in their controls (p=0.811). The annual increase in systolic blood pressure among the cases was 0.60 mmHg 0-7 years before death and 0.22 mmHg 8-14 years before death. The diastolic blood pressure did not significantly increase in either the cases or in controls. Conclusion : These results support that both the long-term blood pressure history and recent increases in blood pressure are associated with the risk of cardiovascular mortality.