Blood pressure and cardiovascular diseases in Chinese adults with type 2 diabetes: A prospective cohort study

Abstract

Background: Controversy persists about the relationship of blood pressure with cardiovascular diseases (CVD) in diabetes and associated disease burden. We assessed these associations among Chinese adults with type 2 diabetes (T2D).

Methods: In 2004-08, the China Kadoorie Biobank recruited >512,000 adults aged 30-79 years from 10 localities across China, including 26,315 with T2D (based on self-report or plasma glucose measurement) but no prior CVD, followed-up for ~9 years. Cox regression yielded adjusted HR for major CVD and all-cause mortality associated with 10 mmHg higher usual (longer-term average) SBP. Attributable fractions were estimated to assess cardiovascular mortality burden due to uncontrolled hypertension (SBP ≥130 mmHg or DBP ≥80 mmHg).

Findings: Overall, 75.7% of participants had self-reported (24.8%) or screen-detected (50.9%) (SBP ≥130 mmHg or DBP ≥80 mmHg) hypertension. Among individuals with self-reported hypertension, 82.3% were treated, of whom 9.3% achieved control. There were positive log-linear associations of blood pressure with CVD, with no evidence of a threshold down to ~120 mmHg for usual SBP. Each 10 mmHg higher usual SBP was associated with HR of 1.28 (95% CI 1.25-1.30), 1.18 (1.15-1.21), 1.17 (1.15-1.19) and 1.45 (1.38-1.52) for cardiovascular death (n=1807), major coronary event (n=1190), ischaemic stroke (n=4362) and intracerebral haemorrhage (n=469), respectively. There was an apparent J-shaped association with all-cause mortality (n=4503). In this diabetes population, uncontrolled hypertension accounted for 39% of cardiovascular deaths.

Interpretation: Uncontrolled hypertension is common in Chinese adults with T2D, resulting in substantial excess risks of CVD. Improved hypertension management could avoid a large number of cardiovascular-related deaths.

Funding: Kadoorie Foundation, Wellcome Trust, MRC, BHF, CR-UK, MoST, NNSF.

Keywords: Blood pressure; Cardiovascular disease; China; Diabetes; Hypertension; Ischaemic heart disease; Stroke.

Fig. 1

Cardiovascular deaths attributable to uncontrolled hypertension among individuals with type 2 diabetes. (a) Adjusted HR for cardiovascular death associated with uncontrolled hypertension (SBP ≥130 mmHg or DBP ≥80 mmHg) by age and sex. HRs are stratified by age-at-risk and study area and are adjusted for education, smoking, alcohol consumption, physical activity and BMI. Squares represent the HR with the area inversely proportional to the variance of the log HR, and error bars indicate the 95%CI. (b) Proportion of cardiovascular deaths attributable to uncontrolled hypertension among individuals with type 2 diabetes. Population attributable fraction (PAF) was calculated as P*([HR−1]/HR), where P is the proportion of individuals with type 2 diabetes who died due to cardiovascular disease with uncontrolled hypertension .

Fig. 2

Associations of usual systolic blood pressure with major cardiovascular diseases and all-cause mortality among individuals with type 2 diabetes. Stratified by age-at-risk, sex and study area and adjusted for education, smoking, alcohol consumption, physical activity and BMI. SBP category cut-points: baseline SBP <115 mmHg, 115 to <135 mmHg, 135 to <150 mmHg, 150 to <165 mmHg, 165 to <180 mmHg, ≥180 mmHg. Squares represent the HR with area inversely proportional to the variance of the log HR, and error bars indicate the 95% CI. Adjusted HRs are plotted against mean usual SBP levels in each category.