Summary
Background
Few studies have evaluated the link between hyperuricaemia and cardiovascular disease in sub-Saharan Africa.
Aims
To assess the prevalence of and factors associated with hyperuricaemia among newly diagnosed treatment-naïve hypertensive patients in sub-Saharan Africa.
Methods
We performed a community-based cross-sectional study from January to December 2012 in Douala, Cameroon (Central Africa). We enrolled newly diagnosed treatment-naïve hypertensive patients, and excluded those with gout or a history of gout. Serum uric acid concentrations were measured by enzymatic colourimetric methods, and hyperuricaemia was defined as a serum uric acid concentration > 70 IU/mL. Fasting blood sugar concentrations, serum creatinine concentrations and lipid profiles were also measured. Logistic regression was used to study factors associated with hyperuricaemia.
Results
We included 839 newly diagnosed treatment-naïve hypertensive patients (427 women and 412 men; mean age 51 ± 11 years; mean serum uric acid concentration 60.5 ± 16.5 IU/L). The prevalence of hyperuricaemia was 31.8% (95% confidence interval [CI] 28.7–34.9) and did not differ by sex (132 women vs. 135 men; P = 0.56). Multivariable logistic regression identified age > 55 years (adjusted odds ratio [AOR] 1.65, 95% CI 1.12–2.29), family history of hypertension (AOR 1.65, 95% CI 1.01–2.67), waist circumference > 102 cm in men or > 88 cm in women (AOR 1.60, 95% CI 1.12–2.29), low-density lipoprotein cholesterol > 1 g/L (AOR 1.33, 95% CI 0.97–1.82) and triglycerides > 1.5 g/L (AOR 1.63, 95% CI 1.01–2.65) as independently associated with hyperuricaemia.
Conclusion
Hyperuricaemia is common among newly diagnosed treatment-naïve hypertensive patients in sub-Saharan Africa and is associated with some components of the metabolic syndrome.
Résumé
Objectif
Évaluer la prévalence et les facteurs associés à l’hyperuricémie chez les patients hypertendus nouvellement diagnostiqués et naïfs de tout traitement antihypertenseur en Afrique sub-saharienne.
Méthodes
Nous avons réalisé une étude transversale de janvier à décembre 2012 en milieu communautaire à Douala, Cameroun. Nous avons inclus tout patient hypertendu nouvellement diagnostiqué et naïf de tout traitement antihypertenseur et exclus tous ceux qui avaient une histoire actuelle ou passée de la goutte et les hypertendus sous traitement. L’hyperuricémie était définie par un taux d’acide urique sérique supérieur à 70 UI/mL. La glycémie à jeun, la créatinimémie et le profil lipidique ont également été mesurés. La régression logistique était utilisée pour étudier les facteurs associés à l’hyperuricémie.
Résultats
Nous avons inclus 839 patients (427 femmes et 412 hommes) nouvellement diagnostiqués hypertendus et naïfs de tout traitement antihypertenseur. L’âge moyen était de 51 (SD : 11) ans, et le taux moyen d’acide urique sérique était de 60,5 (SD : 16,5) UI/L. La prévalence de l’hyperuricémie était de 31,8 % [IC95 % : 28,7 %–34,9 %], et ne diffère pas selon le sexe (femmes, n = 132 vs hommes, n = 135 ; p = 0,56). En régression logistique multivariée, l’âge > 55 ans (AOR : 1,65 [1,12–2,29]), le tour de taille > 102 chez les hommes et 88 chez les femmes (AOR : 1,60 [1,12–2,29]), le cholestérol LDL > 1 g/L (AOR : 1,33 [0,97–1,82]), les antécédents familiaux d’hypertension (AOR : 1,65 [1,01–2,67]), et les triglycérides > 1,5 g/L (AOR : 1,63 [1,01–2,65]) étaient indépendamment associés à l’hyperuricémie.
Conclusion
L’hyperuricémie est fréquente chez les patients hypertendus nouvellement diagnostiqués et naïfs de tout traitement antihypertenseur en Afrique sub-saharienne.
Background
Hypertension affects about 1 billion people in the world, 10–21% of whom live in sub-Saharan Africa . The prevalence of hypertension in Cameroon was 24% in 2010 . Many traditional risk factors associated with hypertension have been identified. However, while hyperuricaemia is known to be a global marker in cardiovascular disease , its role as an independent cardiovascular risk factor is controversial. Hyperuricaemia is generally known to be associated with components of the metabolic syndrome, such as diabetes, dyslipidaemia, obesity and hypertension . For many years, hyperuricaemia has been associated with the risk of developing hypertension . It has been experimentally proven that hyperuricaemia evolving for at least 5 years can cause renal abnormalities, which may lead to hypertension and cardiovascular complications . The prevalence of hyperuricaemia has been estimated at 25% in hypertensive patients naïve to antihypertensive therapy ; nevertheless, hyperuricaemia itself is still not considered to be a classic cardiovascular risk factor. Most data have come from developed countries, with few studies having evaluated the link between hyperuricaemia and cardiovascular disease in sub-Saharan Africa ; because of this, we aimed to describe the prevalence of and factors associated with hyperuricaemia among newly diagnosed hypertensive treatment-naive patients, in the city of Douala, Cameroon (sub-Saharan Africa).
Methods
We conducted a cross-sectional study in the city of Douala, the economic capital of Cameroon (Central Africa), from January to December 2012. This study was performed in accordance with the ethical principles of the Declaration of Helsinki and was approved by the ethics committee of our hospital.
We enrolled all newly diagnosed consecutive hypertensive patients without antihypertensive drug intake from four healthcare centres. Patients with a history of gout or current gout were not included. A standardized case-report form was used for data collection, including sociodemographic, clinical and biological data. Blood pressure was measured after a 5-minute rest – 15 minutes for those with elevated values – in a seated position using a calibrated aneroid manometer, and the diagnosis of hypertension was established after three consecutive measurements. Hypertension was defined as systolic blood pressure > 140 mmHg and/or diastolic blood pressure > 90 mmHg . Treatment-naïve patients were defined as those who had never received any antihypertensive drug. Blood samples were collected after an 8-hour overnight fast, and were sent to the biochemistry laboratory at Douala General Hospital for analysis. Plasma creatinine, fasting blood sugar, total cholesterol (TC), triglycerides (TG) and high-density lipoprotein cholesterol (HDL-C) were measured using enzymatic colourimetric methods; low-density lipoprotein cholesterol (LDL-C) was calculated using the Friedewald formula (LDL-C = TC − HDL-C − TG/5, if TG < 4 g/L).
Operational definitions
Hyperuricaemia was defined as blood uric acid concentration > 70 mg/L . Diabetes was defined as fasting blood sugar concentration > 1.26 g/L and/or antidiabetic drug intake . The lipid profile was classified using the National Cholesterol Education Program in Adult Treatment Panel III (NCEP ATPIII) cut-offs as follows: TC < 2 g/L; LDL-C < 1 g/L; HDL-C > 0.40 g/L; and TG < 1.5 g/L .
Statistical analysis
We used STATA 12.0 for Windows (STATA Corp., College Station, TX, USA) for the data analysis. Quantitative variables are presented as means ± standard deviations; qualitative variables are presented as absolute numbers and percentages. Statistical comparisons were made with Student’s t -test for continuous variables and the Chi 2 test for categorical variables. Factors associated with hyperuricaemia were analysed by univariate logistic regression, reporting odds ratios (ORs) and their 95% confidence intervals (CIs). All significant variables were mutually adjusted for each other in a final multivariable logistic regression model, after dropping one variable in a pair of highly correlated factors (to account for collinearity). A P -value < 0.05 was used to indicate statistically significant results.
Results
During the study period, 839 patients (427 women and 412 men) were diagnosed with hypertension and were naïve to antihypertensive drug treatment. Among them, 76 were known hypertensive patients who were only on lifestyle changes (salt restriction in all cases). The baseline characteristics of the study population are summarized in Table 1 ; data are shown with a sex stratification.
| Variables | Overall ( n = 839) | Women ( n = 427) | Men ( n = 412) | P a |
|---|---|---|---|---|
| Age (years) | 50.9 ± 11.0 | 51.4 ± 11.3 | 50.4 ± 10.8 | 0.189 |
| Diabetes | 65 (7.7) | 34 (8.0) | 31 (7.5) | 0.897 |
| History of hypertension | 76 (9.1) | 34 (8.0) | 42 (10.2) | 0.280 |
| Education | ||||
| None | 12 (1.4) | 7 (1.6) | 5 (1.2) | |
| Primary school | 90 (10.7) | 62 (14.5) | 28 (6.8) | < 0.0001 |
| Secondary school | 461 (54.9) | 260 (60.9) | 201 (48.8) | |
| Tertiary education | 276 (32.9) | 98 (22.9) | 178 (43.2) | |
| Classification of hypertension (JNC7) | ||||
| Systolic blood pressure (mmHg) | 167 ± 16 | 166 ± 17 | 168 ± 16 | 0.029 |
| Diastolic blood pressure (mmHg) | 100 ± 11 | 99 ± 11 | 101 ± 11 | 0.076 |
| Stage 1 | 223 (26.6) | 131 (30.7) | 92 (22.3) | |
| Stage 2 | 616 (73.4) | 296 (69.3) | 320 (77.7) | 0.317 |
| Smoking | 47 (5.6) | 13 (3.0) | 34 (8.2) | 0.001 |
| Waist circumference (cm) | 93 ± 36 | 95 ± 49 | 91 ± 16 | 0.125 |
| Body mass index (kg/m 2 ) | 30.0 ± 5.8 | 30.7 ± 6.4 | 29.3 ± 5.1 | 0.0005 |
| Fasting blood glucose (g/L) | 1.01 ± 0.30 | 0.99 ± 0.33 | 1.02 ± 0.26 | 0.273 |
| Hyperuricaemia | 267 (31.8) | 132 (49.4) | 135 (50.6) | 0.56 |
| Uricaemia (IU/L) | 60.5 ± 16.5 | 56.0 ± 15.2 | 65.1 ± 16.5 | < 0.0001 |
| TC (g/L) | 1.92 ± 0.49 | 1.94 ± 0.52 | 1.90 ± 0.46 | 0.202 |
| HDL-C (g/L) | 0.62 ± 0.26 | 0.64 ± 0.27 | 0.59 ± 0.24 | 0.003 |
| LDL-C (g/L) | 1.15 ± 0.46 | 1.18 ± 0.46 | 1.12 ± 0.45 | 0.048 |
| TG (g/L) | 0.95 ± 0.44 | 0.91 ± 0.40 | 0.99 ± 0.48 | 0.007 |
| eGFR (mL/min) | 94.4 ± 33.3 | 94.1 ± 34.6 | 94.8 ± 31.9 | 0.769 |
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