Abstract P226: Changes of Blood Pressure and Urinary Sodium Over 18 Years in Rural China: Results From the INTERMAP China Prospective Study

Background: Tremendous dietary pattern changes could be a driver of the increasing burden of high blood pressure (BP) in developing countries. However, data on nutrition transitions and associated BP changes are scarce. Objective: To explore BP changes and sodium (Na) consumption over 18 years in China. Methods: International Collaborative Study of Macro-/Micro-nutrients and Blood Pressure (INTERMAP) enrolled 839 men and women aged 40-59 years from three geographically diverse regions (Beijing, Shanxi in the north and Guangxi in the south) in 1997. INTERMAP China Prospective (ICP) Study followed up these three populations in 2015-2016. Seated BP were measured at least twice following at least 5 minutes of rest, using a random zero sphygmomanometer for the INTERMAP (baseline) and an oscillometric device (Omron HEM-907) for the ICP (follow-up). When calculating BP changes, baseline values were converted using equations developed in a calibration study. Timed 24-hr urine samples were collected at baseline and follow-up using the same protocol. Urinary Na and creatinine (Cr) were measured by emission flame photometry method at baseline and ion-selective electrode method at follow-up. BP and dietary Na changes over time were compared using student t test. Results: Systolic BP increased considerably in all three sites; largest increment in Guangxi (18.6, 95% CI: 16.0-21.1 mm Hg, P<0.001) and smallest in Beijing (9.1, 6.3-11.8 mm Hg, P<0.001) (Table 1). Level of urinary Na was almost double in north (Beijing and Shanxi) than south (Guangxi) at follow-up (P<0.001), similar as baseline. On average, participants consumed 10.8 (4.7) and 11.8 (4.7) grams of salt at Beijing and Shanxi and 6.3 (3.0) grams of salt at Guangxi at follow-up, though a trend of reduction in Na/Cr (-3.7, 95% CI: -4.7- -2.6, P<0.001) overall was documented. Conclusions: Systolic BP levels increased considerably in this cohort between 1997 and 2015 in rural China. Na consumption might have a declining trend, but still at a very high level at northern China.