Revisiting the association of blood pressure with mortality in oldest old people in China: community based, longitudinal prospective study

Abstract

Objective: To examine the associations of blood pressure with all cause mortality and cause specific mortality at three years among oldest old people in China.

Design: Community based, longitudinal prospective study.

Setting: 2011 and 2014 waves of the Chinese Longitudinal Healthy Longevity Survey, conducted in 22 Chinese provinces.

Participants: 4658 oldest old individuals (mean age 92.1 years).

Main outcome measures: All cause mortality and cause specific mortality assessed at three year follow-up.

Results: 1997 deaths were recorded at three year follow-up. U shaped associations of mortality with systolic blood pressure, mean arterial pressure, and pulse pressure were identified; values of 143.5 mm Hg, 101 mm Hg, and 66 mm Hg conferred the minimum mortality risk, respectively. After adjustment for covariates, the U shaped association remained only for systolic blood pressure (minimum mortality risk at 129 mm Hg). Compared with a systolic blood pressure value of 129 mm Hg, risk of all cause mortality decreased for values lower than 107 mm Hg (from 1.47 (95% confidence interval 1.01 to 2.17) to 1.08 (1.01 to 1.17)), and increased for values greater than 154 mm Hg (from 1.08 (1.01 to 1.17) to 1.27 (1.02 to 1.58)). In the cause specific analysis, compared with a middle range of systolic blood pressure (107-154 mm Hg), higher values (>154 mm Hg) were associated with a higher risk of cardiovascular mortality (adjusted hazard ratio 1.51 (95% confidence interval 1.12 to 2.02)); lower values (<107 mm Hg) were associated with a higher risk of non-cardiovascular mortality (1.58 (1.26 to 1.98)). The U shaped associations remained in sensitivity and subgroup analyses.

Conclusions: This study indicates a U shaped association between systolic blood pressure and all cause mortality at three years among oldest old people in China. This association could be explained by the finding that higher systolic blood pressure predicted a higher risk of death from cardiovascular disease, and that lower systolic blood pressure predicted a higher risk of death from non-cardiovascular causes. These results emphasise the importance of revisiting blood pressure management or establishing specific guidelines for management among oldest old individuals.

Fig 1

Associations of blood pressure with three year all cause mortality in study population of Chinese oldest old people, in Cox models with penalised splines after adjustment. Lines=estimated hazard ratio of systolic blood pressure (129 mm Hg reference), diastolic blood pressure (80 mm Hg), mean arterial pressure (90 mm Hg), and pulse pressure (57.5 mm Hg) for risk of three year all cause mortality; dotted lines=95% confidence intervals; df=degrees of freedom

Fig 2

Hazard ratio (95% CI) for three year all cause mortality at different levels of systolic blood pressure (80-190 mm Hg) in Cox models with penalised splines after adjustment (129 mm Hg reference), in study population of Chinese oldest old people

Fig 3

Associations of systolic blood pressure with three year cardiovascular and non-cardiovascular mortality risk in study population of Chinese oldest old people, in Cox models with penalised splines after adjustment. Lines=estimated hazard ratio of systolic blood pressure (129 mm Hg reference) for three year cardiovascular and non-cardiovascular mortality; dotted lines=95% confidence intervals