| 21. |
- Brunström, Mattias, et al.
(författare)
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Standardization according to blood pressure lowering in meta-analyses of antihypertensive trials : comparison of three methodological approaches
- 2018
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Ingår i: Journal of Hypertension. - : Lippincott Williams & Wilkins. - 0263-6352 .- 1473-5598. ; 36:1, s. 4-15
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Forskningsöversikt (refereegranskat)abstract
- OBJECTIVE: Assess how standardization of relative risks (RRs) and standard errors (SEs), according to blood pressure differences within trials, affects heterogeneity, overall effect estimates and study weights in meta-analyses of antihypertensive treatment.METHOD: Data from a previous systematic review were used. Three sets of analyses were performed, using both random-effects and fixed-effects model for meta-analyses. First, we used raw data from the included trials. Second, we standardized RRs as if SBP was reduced by 10 mmHg in all trials. Third, we standardized both RRs and SEs.RESULTS: When RRs were standardized according to blood pressure lowering, heterogeneity between trials increased (I = 36 vs. 93% for mortality). This conferred large differences in treatment effect estimates using random-effects and fixed-effects model (RR 0.79, 95% confidence interval 0.70-0.89, respectively, 0.97, 0.94-0.99). When SEs were standardized, confidence intervals for individual trials widened, resulting in lower power to detect heterogeneity across trials. Study weights were dissociated from number of events in trials (P < 0.0001, R = 0.99 before standardization vs. P = 0.063, R = 0.05 after standardization). This induced a secondary shift in weight from trials with lower baseline SBP to trials with higher baseline SBP, resulting in exaggerated overall effect estimates.CONCLUSION: Standardization of RRs exaggerates differences between trials and makes meta-analyses highly sensitive to choice of statistical method. Standardization of SEs masks heterogeneity and results in biased effect estimates.
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| 24. |
- Carlberg, Bo
(författare)
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Is lower really better? : Issue of the J curve hypothesis in hypertension
- 2016
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Ingår i: Journal of Hypertension. - : Wolters Kluwer. - 0263-6352 .- 1473-5598. ; 34, s. e196-
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Tidskriftsartikel (refereegranskat)abstract
- The J curve hypothesis propose that the relation between blood pressure and risk for cardiovascular events is non-linear. Instead of a decreased risk with lower blood pressure, the risk increases at lower blood pressures. This issue has been discussed for many years, and is still a hot topic. The debates have most often had its origin in the question about how far blood pressure should be lowered with antihypertensive drugs.One one hand, we know that many patients with hypertension is not treated to targets according to guidelines and that this contributes to the high risk for cardiovascular diseases in patients with hypertension. On the other hand, overtreatment could be one reason for the subobtimal effect of antihypertensive drugs on cardiovascular diseases.The issue about a J curve in the effect of antihypertensive drugs is complicated.The relation between blood pressure and cardiovascular risk is different for different cardiovascular outcomes. For example, the risk for intracerebral hemorrhage seem to increase steeper at higher blood pressure than for most other outcomes. On the other hand, the risk for abdominal aortic aneurysm increases only modestly with higher blood pressure. In addition, end stage renal disease and cognitive decline could have other relations between blood pressure and risk. Age, cardiovascular disease and diabetes have also been found to modify the relation between risk and outcome.Earlier this year, we published a meta-analysis of randomized controlled trials with antihypertensive drugs in patients with diabetes mellitus (ref). Included trials had to compare treatment with an antihypertensive drug against placebo, two antihypertensive agents against one or one blood pressure target against another target. The studies were stratified according to blood pressure at randomization (baseline blood pressure), mimicking the situation you as a clinician meet when you decide to recommend a patients additional antihypertensive therapy or not. We contacted authors to receive data from diabetic subgroups in large studies. Thus, we were able to include more studies than in previous systematic reviews in this field. All together, we included data from 49 randomized controlled trials, including 73 738 patients.The systematic review showed that the effect of antihypertensive drugs on cardiovascular outcomes is different at different blood pressure levels. For most outcomes, adding antihypertensive drugs were beneficial in patients with diabetes mellitus and high blood pressure. However, this benefit decreased with decreasing blood pressure. The risk for cardiovascular death increased when therapy was added in patents with diabetes and systolic blood pressure below 140 mmHg. The benefits of adding antihypertensive treatment at different blood pressure levels are summarized in the figure below.Thus, in patients with diabetes, the relations between treatment effect of antihypertensive drugs are different at different blood pressure levels. Treatment effects differ for different cardiovascular outcomes. These data question previous guidelines that recommend a systolic blood pressure target below 130 mmHg in patients with diabetes mellitus.In a very recent systematic review, we have reexamined the relation between randomization blood pressure and cardiovascular stratified for different baseline blood pressures. The meta-analyses include patients with and without diabetes, with and without previous cardiovascular disease etc. Altogether, 58 trials with 290 000 patients were included. The study shows that the effect of blood pressure lowering on cardiovascular outcomes is dependent on baseline systolic blood pressure but also differ between different subsets of patients. This study is under review and the results will be presented during the lecture.
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| 27. |
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| 28. |
- Carlström, Mattias, et al.
(författare)
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Angiogenesis inhibition causes hypertension and placental dysfunction in a rat model of preeclampsia
- 2009
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Ingår i: Journal of Hypertension. - 0263-6352 .- 1473-5598. ; 27:4, s. 829-837
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Tidskriftsartikel (refereegranskat)abstract
- Background Preeclampsia is a serious pregnancy complication, accompanied by increased maternal and fetal morbidity. Different models have been used to study preeclampsia, but none of these display all the key features of the disease. Method We investigated the effects on maternal blood pressure and fetal outcome exerted by the angiogenesis inhibitor Suramin (1100 mg/kg i.p.) during early placentation. Blood pressure and heart rate were measured continuously with telemetry in Sprague - Dawley rats of four experimental groups: nonpregnant controls, Suramin-treated nonpregnant rats, pregnant controls and pregnant Suramin-treated rats. Blood samples were collected before pregnancy and at gestational day 20 for analysis of renin and sFIt-1. The fetal and placental morphology were evaluated after caesarian section on gestational day 20. Results The blood pressure of the pregnant Suramin-treated rats successively increased during pregnancy and differed by 17 mmHg at gestational day 20 compared with the pregnant control rats. In the pregnant Suramin-treated rats group, the renin levels increased (+122%) and the sFIt-1 levels decreased (-58%) during pregnancy. The pregnant Suramin-treated fetuses and placentae were smaller (2.8 g and 0.51 g) than the pregnant controls rats' fetuses and placentae (3.5g and 0.56g). Resorptions tended to be higher in the pregnant Suramin-treated rat litters compared with the pregnant control rat litters (P = 0.08). The area of the maternal blood vessels in the mesometrial triangle was smaller in the pregnant Suramin-treated rats group than in the pregnant control rats group. Conclusion The inhibition of uterine angiogenesis increases maternal blood pressure and compromises fetal and placental development. Placental hypoxia and subsequent activation of the renin-angiotensin system may play an important role for the hypertension. J Hypertens 27:829-837 (C) 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins.
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| 29. |
- Carlström, Mattias, et al.
(författare)
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Hydronephrosis causes salt-sensitive hypertension in rats
- 2006
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Ingår i: Journal of Hypertension. - : Ovid Technologies (Wolters Kluwer Health). - 0263-6352 .- 1473-5598. ; 24:7, s. 1437-1443
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Hypertension is a common disease in the Western world and approximately 5% of all cases are secondary to kidney malfunction. It is not clear whether unilateral hydronephrosis due to partial obstruction affects blood pressure. AIM: The aim of this study was to determine whether hypertension develops and to investigate the effects of different salt diets on the blood pressure in hydronephrotic animals. METHODS: Unilateral partial ureteral obstruction was created in 3-week-old Sprague-Dawley rats. A telemetric device was implanted 4-6 weeks later and blood pressure was measured on normal, low- and high-salt diets. Plasma samples were collected on all diets for renin analysis. RESULTS: All hydronephrotic animals developed hypertension that correlated to the degree of hydronephrosis. The blood pressure increased slowly with time and was salt sensitive. In severe hydronephrosis, blood pressure increased from 118 ± 5 mmHg on low salt to 140 ± 6 mmHg on high salt intake, compared to control levels of 82 ± 2 and 84 ± 2 mmHg, respectively. Plasma renin concentration was increased in the hydronephrotic group of animals compared to controls on all diets, but the difference was only significant on a normal salt diet, 165 ± 15 versus 86 ± 12 μGU/ml respectively. In animals with severe hydronephrosis the plasma renin levels were lower, and the changes less, than in those with mild and moderate hydronephrosis. CONCLUSION: This study demonstrates the presence of a salt-sensitive hypertension in hydronephrosis. A systemic effect of the renin-angiotensin system alone cannot be responsible for the hypertension.
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