Abstract High serum uric acid (sUA) has been reported to be a risk factor for hypertension however. Uric acid and hypertension: an age-related relationship ?. Serum uric acid (SUA) level has been shown to be associated with . The relationships remained significant after adjustment for age and sex. Reducing levels of uric acid in blood lowered blood pressure to normal in most teens in a study designed to investigate a possible link between.
The association of hyperuricemia with hypertension has long been recognized with early investigators such as Frederick Mahomed [ 1 ], Alexander Haig [ 5 ], and Nathan Smith Davis [ 67 ], hypothesizing that uric acid might be a cause of hypertension or renal disease. Uric acid is thought to play a pathogenic role in hypertension mediated by several mechanisms such as inflammation, vascular smooth muscle cell proliferation in renal microcirculationendothelial dysfunction and activation of the renin — angiotensin — aldosterone system [ 8 - 11 ].
Furthermore, studies have shown that in overweight and obese subjects, hyperinsulinemia secondary to insulin resistance may enhance the reabsorption of uric acid and thus contribute to the association of hyperuricemia with hypertension [ 12 ].
The increasing prevalence of hypertension in Cameroon [ 13 - 15 ] coupled with the forecast that by the yearnon-communicable diseases such as cardiovascular diseases will be the major causes of morbidity and mortality in developing countries, accounting for almost four times as many deaths as from communicable diseases [ 16 ] warrant that weight be assigned to the individual risk factors of hypertension and the existence of any possible interaction between them as this will improve the efficiency of prevention strategies.
However given that the results linking uric acid and hypertension are not entirely consistent [ 1718 ], this study was carried out to investigate the relationship between uric acid and hypertension in Cameroonian adults.
Methods Study population The study participants constituted of individuals with hypertension 20 years and above and apparently healthy people 20 years and above who served as controls and consented to be part of the study. Sensitization was done through announcements in local churches and radio stations in the communities, asking willing participants to come to the health facilities Limbe Regional Hospital and Buea Regional Hospital following an overnight fast.
Volunteers were assisted to complete a structured questionnaire that contained information on general state of health, physical activity, smoking, alcohol consumption and dietary patterns. It was a cross-sectional study carried out from April —September After seeking and obtaining informed consent from each participant. All participants were individually interviewed with a structured questionnaire and information on gender, age, weight, height, waist circumference, hip circumference, smoking status, physical exercise status and diet was recorded.
Fasting blood samples were then collected for the measurement of uric acidglucose, lipids and creatinine.
Written consent was obtained from each individual before enrolment. Blood pressure measurement Blood pressure was measured 3 times consecutively in the right arm placed at the heart level using an automatic blood pressure measuring device OMRON OMRON, Hoofdorrp, The Netherlands after the subjects had rested for at least 10 minutes in a sitting position.Why Diabetics Get High Blood Pressure
The measurements were taken 60 seconds apart and the average systolic and diastolic blood pressures were recorded and used for our analyses. Measurement of biochemical markers Venous blood samples were drawn from all participants after an overnight fast h after which they were allowed to clot at room temperature for h and the serum separated by centrifugation for 15 min at rpm.
From these samples, uric acid, triglycerides, cholesterol, HDL- cholesterol and creatinine were measured. Glucose was measured from venous blood collected into a sodium fluoride tube. LDL-cholesterol was calculated using the Friedewald equation and the estimated glomerular filtration rate was calculated using the Croft-Gault formula [ 20 ]. All biochemical assays were analyzed enzymatically on a spectrophotometer Fortress Diagnostics alongside human control sera.
Results General characteristics of study population The main clinical and anthropometric characteristics of the study population are represented in Supplementary Table 1.
A total of individuals 20 years and above from Fako Division, South-West Region were recruited for this study.
It was made up These participants were divided according to their blood pressure status into hypertensive, pre-hypertensive and normotensive. The mean age of study participants was The mean systolic blood pressure was The average uric acid concentration was 5. Association between uric acid and hypertension Supplementary Table 2 displays the prevalence of uricaemia with blood pressure category.
Of this number, 47 No body with a normal BP had a high UA concentration. Subjects were then placed in serum uric acid quartiles and their mean systolic and diastolic blood pressures compared.
Association between uric acid and other hypertension risk factors The association between uric acid and other risk factors of hypertension was analyzed. Discussion Hypertension is an increasingly important medical and public health issue worldwide, affecting approximately one billion individuals [ 19 ]. As a major risk factor for cardiovascular and renal morbidity and mortality, hypertension is one of the leading contributors to global disease burden, with its current prevalence in many developing countries, particularly in urban societies already as high as those seen in developed countries [ 21 ].
To be able to curb this rising prevalence it is necessary to study the individual risk factors and the possible existence of interaction between them.
Relationship between uric acid and blood pressure in different age groups
Evidence from a number of studies [ 22 - 24 ] suggest that uric acid be added to the list of conventional risk factors of hypertension like obesity [ 2526 ], age [ 2728 ] renal disease [ 1029 ], diabetes mellitus [ 3031 ].
Uric acid has been implicated in hypertension through the probable role it is thought to play in mediating hypertension via mechanisms like inflammation, vascular smooth muscle cell proliferation in renal microcirculation, endothelial dysfunction and activation of the rennin — angiotensin — aldosterone system [ 8 ]. Given that not all epidemiological studies support uric acid as an independent risk factor for hypertension [ 18 ] coupled to the little or no information on the relationship between uric acid and hypertension in Cameroon was the reason why this study was carried out.
The prevalence of hypertension grows higher with aging, resulting in an increase in morbidity and mortality through various events such as myocardial infarction, heart failure, stroke, and renal failure [ 1 - 4 ]. Hyperuricemia has been proposed to have an association with hypertension in various studies.
Serum uric acid UA levels were demonstrated to be an independent predictor for developing hypertension [ 5 - 7 ]. Regardless of the different ethnic origins, a continuous relationship between serum UA and blood pressure BP was observed in African-Americans and whites [ 89 ] as well as in Asians [ 710 ] including Koreans [ 11 - 13 ].
For determining the causal role of serum UA in the development of hypertension, Mazzali et al. Reduction of serum UA was associated with a decrease in BP through the regulation of renin-angiotensin and nitric oxide system [ 15 ].
Relationship between uric acid and blood pressure in different age groups
Taking this into account, a hypothesis regarding the effect of serum UA-lowering agents which could have potential benefits in prevention and treatment of hypertension has emerged. Feig and Johnson [ 1 ] showed a high correlation between serum UA and BP in childhood primary hypertension and demonstrated promising results using allopurinol, a UA-lowering agent, to reduce BP in adolescents with newly developed hypertension in a pilot study [ 16 ].
Early intervention of controlling serum UA was proposed to have effect on delaying the progression of early hypertension. However, studies specifically of elderly patients have had controversial results regarding the relation between serum UA and BP [ 1718 ]. Also, the use of UA-lowering agents did not have effect on controlling BP in the elderly as in the adolescents [ 19 ].
Taken together, the relationship between serum UA and BP was known to be weakened by the aging process, but there were no studies confirming in which age group the relationship would be the strongest. Also, studies mentioned above lack control over variables which could have effect on serum UA levels such as the history of taking diuretics, antihypertensive medication or other drugs, obesity, and renal function.