Age-specific relation of blood pressure to vascular and non-vascular chronic disease in China: a prospective study of 0.5 million adults

Background The age-specific relation of blood pressure to vascular disease has been studied mostly in Western populations, and prior to the widespread use of brain imaging for diagnosis of stroke types (ischaemic stroke and intracerebral haemorrhage). Methods In 2004-08, 512,891 adults (59% women) were recruited into a prospective study in China. During a mean follow-up of 9 years, there were 85,007 incident vascular and non-vascular chronic disease events (91% of strokes had brain imaging). Cox regression yielded adjusted hazard ratios (HRs) relating systolic blood pressure (SBP) to disease incidence. HRs were corrected for regression dilution to estimate associations with long-term average (‘usual’) SBP. Findings At ages 40-79, usual SBP was continuously and positively associated with incident major vascular disease throughout the range 120-180 mmHg: each 10 mmHg higher usual SBP was associated with ~30% higher risk of ischaemic heart disease (HR 1·31 [95%CI 1·28-1·34]) and ischaemic stroke (1·30 [1·29-1·31]), but the association with intracerebral haemorrhage was about twice as steep (1·68 [1·65-1·71]). HRs for vascular disease were twice as extreme at ages 40-49 than 70- 79. Usual SBP was also positively associated with incident chronic kidney disease and diabetes. Interpretation Among Chinese adults, SBP was continuously related to major vascular disease with no evidence of a threshold down to 120 mmHg. Unlike previous studies in Western populations, blood pressure was more strongly associated with intracerebral haemorrhage than ischaemic stroke. About half of all vascular deaths in China were attributable to elevated blood pressure, accounting for ~1 million deaths (<80 years) annually.