| Background and objectiveHypertension has caused 5% of the disease burden throughout the world and been thought as one of the major public health problem. It is believed that many risk factors could responsible for increasing prevalence of the hypertension, such as the extension of life span, obesity/overweight, physical inactivity and unhealthy diet. During the development of the disease, hypertension leads to the organs damages such as heart, brain and kidney. It was found that there is a J shaped curve association between the mortality in the elderly and blood pressure.The harm of hypotension is often ignored by researchers. There are various clinical manifestations, most are neuropsychiatric symptoms, such as fatigue, weakness, headache and depression. Recently some studies find that there is an association between hypotension and other disease, one of which is cardiovascular disease contributing to the mortality.Most of the revelant studies have been conducted among populations of Western Europe and North America. Despite the Asian account for more than 60% of the world population, the relationship between blood pressure level and the death of them has not been explored. To resove these controversial problem, we evaluated the relationship between blood pressure level and the risk of all-cause death and cause-specific death. Our study, which was based on the data from the Electronic Health Records of Yinzhou District during 2005 to 2014, was a cohort involving around 45 thousand participants.Material and methodsThe data of participants was extracted from the Electronic Health Records of 5 representative towns in Yizhou District between January 2005 and December 2009. A total of 77374 residents aged 18 years or older were available for recuitment, of which 44611 participants could be followed, including 19573 men and 25038 women.The response rate of our study was 57.66%. All deaths that ocurred before July 2014 were included for analysis.We used systolic blood pressure (SBP) and diastolic blood pressure (DBP) to define blood pressure groups for the analysis. We defined SBP<90mmHg and (or) DBP<60mmHg as hypotension group,90mmHg≤SBP<140mmHg and 60mmHg≤DBP<90mmHg as normal group,140mmHg<SBP<160mmHg and (or) 90mmHg≤DBP<100mmHg as grade 1 hypertension group,160mmHg<SBP<180mmHg and (or) 100mmHg≤DBP<110mmHg as grade 2 hypertension group, SBP≥180mmHg and (or) DBP≥110mmHg as grade 3 hypertension group. The normal group was regraded as the reference group in our study.Hazard ratios (HRs) of mortality were estimated through cox proportional hazard regression analysis for different blood pressure groups with a maximum follow-up of 9.56 years. To minimize the influence of possible effect of bias, we also made the stratified analyses and sensitivity analyses. All the statistical analyses were completed by SAS Version 9.2 (SAS Institute, Gary, NC, USA). The significance level was P< 0.05.ResultsA total of 44611 participants were included in our analysis, and during a mean follow-up period of 8.48 years,1064 people (613 men and 451 women) died. The all-cause mortality was 281.10 per 100000 person-years.We found that grade 3 hypertension group suffered an increased risk of all-cause mortality for both men and women. After adjustment for age and sex, the grade 3 hypertension was associated with an increased risk of all-cause mortality in this cohort compared with the normal group; the HR of hypotension group and grade 3 hypertension group were in 1.42 (95% confidence interval:1.05-1.90) and 1.33 (95% confidence interval:1.03-1.71). And after the adjustment of multi-factors, the strongly association between grade 3 hypertension and increased mortality still remained, with HR of 1.39 (95% confidence interval:1.07-1.79). Besides, we observed a U-shaped association between blood pressure and all-cause mortality.Parallel results were observed in the following stratified analysis by sex, age (18-60 or>60 years) and follow-up time (< 8years or≥8 years). The residents in hypotension group had the highest mortality risk of all-cancer, while the grade 1 hypertension group showed the lowest all-cancer mortality risk.We observed a similar U-shaped association between blood pressure and risk of cardiovascular disease mortality. Even after excluding participants who were current smokers or participants in less than five years of follow-up, the association also existed.ConclusionThere was a U-shaped curve association between blood pressure and mortality among Chinese adults. Adults from hypotension and grade 3 hypertension groups had the highest risk of deaths. Our finding could provide informative suggesstion for public health policies focusing on the control of blood pressure abnormalities. |
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