Prospective Study Of Relationship Between Blood Pressure And Kidney Dysfunction In Rural Chinese Adults

BackgroundMany prospective epidemiology studies verify that hypertension is an independent risk factors of chronic kidney disease (CKD) and the progression. CKD has brought an enormous burden global wide including China, which rural population compromised of more than 70%. At the same time, people in this area shared a low medical care and less conscious of disease compared urban. It is necessary to take a look in this special area to verify the risk factors of chronic kidney disease in order to take a measure to prevent seriously kidney damage and progress as well as reduce the rate of morbidity and mortality caused by cardiovascular disease.MethodsA large community based population study aged 40-60 years conducted in rural areas in Anqing enrolled participants between 2003 and 2005 with informed consent and with a number of 3602 participants had a follow-up. The participants those with seriously damaged organ dysfunction such as apoplexy, cancer and coronary disease self-reported diabetes and hypertension were excluded. We took both questionnaire and physical examination on the patients and the physical examination including anthropometric indicators and laboratory tests. The questionnaire took a record of the socio-demographic characteristics, lifestyle, medical history, and family history of the disease, and treatment of disease history and so on. At the same time a standard operating program (SOP) to measure the blood pressure. Multiple linear regression or logistic regression were used to investigate the association between blood pressure (BP)and annual estimated glomerular filtration rate (eGFR) change and rapid kidney function decline defined as annual eGFR change was more than 3 ml/min/1.73m2. Furthermore we examined if the associations varied by baseline eGFR strata. eGFR was calculated from the equation of CKD-EPI and the category of blood pressure was stratified according to JNC-7. Two-tailed P<0.05 were considered statistically significant in all analyses. R software version 3.01 (https://www.R-project.org/) was used to perform all statistical analyses.Results(1) The study included 2383 participants,1237 were males with a percentage of 51.9% and 1146 were females.461 patients had a rapid renal function decline and the percentage in males and females separately is 21.3% and 17.3%. Men had a higher age (50.1±5.1 vs 48.8±5.2岁, P<0.001 and higher diastolic blood pressure (79.1±11.4 vs 77.2±10.7, P<0.001) than women at baseline. Females had a higher baseline eGFR (107.8±12.9 vs 110.1±13.5 ml/min/1.73m2,P<0.001). There was no difference in systolic blood pressure (124.1±17.3 vs 124.0±17.9mmHg, P=0.890).Among 1237 male participants, about 16.3% had a systolic blood pressure (SBP) more than 140mmHg and the percentage in females is 17.5%. The percentage of the level of diastolic blood pressure (DBP) more than 90mmHg is 16.5% in males; 11.9% in females. The current smoker (72% vs 2.7%, P<0.001) and current alcohol drinker (46.6% vs 2.7%, P<0.001) was higher for male patients.(2)The mean blood pressure is not equally in different age group (P<0.05) and was increased with aging. In males eGFR annual change was increased with SBP and DBP increasing and not in females.(3)Although both genders showed an increased eGFR annual change with blood pressure risen. But the trend was only significant in males (P=0.001 in SBP groups and P=0.007 in DBP groups) not in females, (P=0.176 in SBP groups and P=0.373 in DBP groups). Compared to SBP<120mmHg, those with SBP≥140mmHg had a 0.53ml/min/1.73m2 (P=0.002) increased annual eGFR change. While those with DBP>90mmHg had a 0.46ml/min/1.73m2 (P=0.006) increased annual eGFR change.(4) In males, compared to the lowest blood pressure category, those with a higher SBP, that is SBP≥120mmHg, the risk for rapid renal decline was significant increased with an odds ratio of 1.75 (95%CI:1.11-2.77), while those with a SBP≥140mmHg, the OR is 2.35. In terms of DBP, DBP≥90mmHg the risk increased 1.84 (95%CI:1.09-3.12). In females, the risk significantly increased when SBP≥130mmHg with an odds ratio of 2.29 (95%CI:1.28-4.12).(5)When stratified by baseline eGFR according to median level(low:<110 vs. high:≥110), he highest annual eGFR change was found in males with low baseline eGFR and SBP≥140mmHg (β=0.63; P=0.015) or DBP≥90mmHg(β=0.61; P=0.007), and there was a significant interaction between baseline SBP/DBPand eGFR on annual eGFR change in males, but not in females.(6)When stratified by baseline eGFR according to median level, the highest risk of rapid eGFR decline was found in males with low baseline eGFR and SBP≥140mmHg (OR=3.0; 95% CI:1.6-5.6) or DBP>90mmHg(OR=2.6; 95%CI: 1.4-4.6), and there was a significant interaction between baseline SBP/DBP and eGFR on renal function decline in males, but not in females.ConclusionsBlood pressure is increased with age in China rural middle-aged population without baseline kidney dysfunction. Men’s kidney function is more vulnerable to blood pressure. There was a dose-response association between baseline SBP/DBP and annual eGFR decline in males without a clear threshold, and such relationship differed remarkably by gender and baseline eGFR level. Males with eGFR<110 were particularly vulnerable to the adverse renal effects of elevated SBP and DBP.BackgroundHypertension is known to be an independent risk factors to chronic kidney disease (CKD) global wide. Adversely, chronic kidney disease can cause hypertension. A national survey in 2010 showed that the prevalence of hypertension in China is 38% and increasing with aging. There is a difference in genders and males were more invulnerable than females. Hypertension is closely associated with CKD and is known to be a major promoter of the decline in estimated glomerular filtration rate (eGFR) in diabetic and non-diabetic kidney disease. Identifing the annual eGFR decline in different blood pressure and hypertensive populations and explore the hypertensive-populations specific correlation between blood pressure and eGFR slope and rapid renal function decline is of clinical and public health significance.MethodA large clinical trial conducted in rural areas in Anqing and Lianyungang enrolled essential hypertension participants aged 45-75 years without kidney disease at baseline between 2008 and 2009 with informed consent and with a number of 6188 participants had a follow-up. The participants those with seriously damaged organ dysfunction such as stroke, cancer and coronary disease were excluded. Finally,4027 participants were included in the analysis. We took both questionnaire and physical examination on the patients and the physical examination including anthropometric indicators and laboratory tests. The questionnaire took a record of the socio-demographic characteristics, lifestyle, medical history, and family history of the disease, and treatment of disease history and so on. At the same time a standard operating program (SOP) to measure the blood pressure. Multiple linear regression and logistic regression were used to investigate the relatioship between blood pressure (BP) and hypertensive populations and annual eGFR decline and rapid renal function decline and incidence of chronic kidney disease. eGFR was calculated from the equation of CKD-EPI and the category of blood pressure was stratified according to Chinese Guidelines for the management of hypertension. Two-tailed P<0.05 were considered statistically significant in all analyses. R software version 3.01 (https://www.R-project.org/) was used to perform all statistical analyses.Results(1) The cohort enrolled a total number of 4027 essential hypertension patients aged 45-75 years old. There were 1150(28.6%) males and 2877(71.4%) females participants. The prevalence of newly diagnosed hypertension patients, without taking anti-hypertensive drug hypertension patients and taking anti-hypertensive medication hypertension patients were 1390(34.5%),1041(25.9%) and 1596(39.6%). Taking anti-hypertensive medication hypertension patients had a higher fasting glucose, triglyceride homocysteine and lower HDL compared to other populations. The prevalence of chronic kidney disease was 171174 (12.5%),130 (12.5%) and 249 (15.6%) (P=0.020) separately in different hypertensive populations.(2) Annual eGFR decline and percentage of annual decline is increased with blood pressure. After adjusted age, sex, center and baseline eGFR, annual eGFR change was (1.66±0.06) ml/min/1.73m2/yrs, (1.79±0.06) ml/min/1.73m2/yrs and (2.11±0.08) ml/min/1.73m2/yrs (P for trend<0.001) separately in SBP groups(<160mmHg,160-179mmHg,≥180mmHg) while the percentage of annual decline(%) was (1.86±0.07), (2.00±0.07) and (2.40±0.10) (P for trend<0.001)(3) The anti-hypertensive medication participants had the highest annual eGFR change and percentage of annual eGFR decline with (1.97±0.06) ml/min/1.73m2/yrs and (1.97±0.06)%, while in newly diagnose hypertension the number was (1.61±0.06)ml/min/1.73m2/yrs and(1.61±0.06)%, (1.81±0.07)ml/min/1.73m2/yrs and (1.81±0.07)% in non-antihypertensive drug use groups.(P for trend<0.001)(4)In full adjusted model, each 10 mmHg increase in SBP, eGFR declined 0.08 ml/min/1.73m2 per year and the risk of having rapid renal function decline was 1.10 (95%CI:1.06-1.14) and was associated with a 13%(95%CI:1.07-1.19) increase in risk of developing chronic kidney disease. Each 10 mmHg increase in DBP, eGFR declined 0.16 ml/min/1.73m2 per year and the risk of having rapid renal function decline was 1.16 (95%CI:1.08-1.24)) and was associated with a 25%(95%CI:1.13-1.37) increase in risk of developing chronic kidney disease.(5) In multivariate models, compared to newly diagnosed patients, those anti-hypertensive medication participants had the highest eGFR decline(0.28 ml/min/1.73m2 per year) and the odds ratio of having rapid renal function decline and developing CKD were 1.28(95%CI:1.03-1.63, P=0.026) and 1.26(95%CI:0.97-1.64) separately.(6) Compared with subjects with a systolic blood pressure less than 160mmHg, those SBP with a range between 160-179 with a more rapid decline in eGFR of an additional 0.16 ml/min per 1.73 m2 per year and the adjusted odds ratio of having rapid renal function decline and developing CKD were 1.21 (95%CI:1.02-1.43, P=0.028) and 1.06(95%CI:0.84-1.36, P=0.613). Those with SBP higher than 180mmHg, with an additional 0.45 ml/min per 1.73 m2 per year eGFR decline and the odds ratio were 1.62(95%CI:1.32-1.99, P<0.001) and 1.86(95%CI:1.39-2.48, P<0.001). Compared to diastolic blood pressure less than 90mmHg, those with a DBP higher than 100mmHg, with a more rapid decline in eGFR of an additional 0.36 ml/min per 1.73 m2 per year and the adjusted odds ratio of having rapid renal function decline and developing CKD were 1.47 (95%CI:1.20-1.80, P<0.001) and 1.78(95%CI:1.34-2.37, P<0.001)ConclusionAnnual eGFR decline, the prevalence of rapid renal function decline and chronic kidney disease was increased with blood pressure in primary hypertension patients in rural China areas. The linear relationship was found between blood pressure and rapid renal function decline and CKD, meanwhile stage III hypertension has the highest risk.