We report the overall prevalence rate of hyperuricemia to be 25% with comparable proportions of males and females having elevated SUA. We note in this report that hyperuricaemic subjects had a comparable mean age with normouricaemic subjects and that the proportion of subjects with hyperuricaemia did not increase with increasing age except for the females in which the proportions of females with elevated SUA increased steeply after 80 years of age. The prevalence of the MetS in the study population was 60% and the proportion of the subjects with the MetS who had hyperuricaemia, was comparable to that of the subjects with MetS who had normouricaemia (92(61%) vs 263 (56%), p = 0.1). The clinical and biochemical parameters that differed between the hyperuricaemic and normouricaemic subjects included, serum TG, smoking histories and waist circumference measurements. The possible predictors of elevated SUA included centripetal obesity, elevated serum TG and a positive smoking history.
SUA acid is a diprotic acid produced by xanthine oxidase from xanthine and hypoxanthine, which in turn are produced from purine [17
]. SUA acid is a strong reducing agent and in humans, over half the antioxidant capacity of blood plasma comes from SUA [17
]. The resultant effects of elevated SUA include gout, Lesch Nyhan's syndrome, and uric acid stones [3
]. The role of hyperuricaemia in DM has been a subject of much debate as some researchers report it to be a resultant effect of DM and others have reported it to be a risk factor for the development of type 2 DM [19
]. Hyperuricaemia has also been found to be associated with insulin resistance and components of the MetS [21
]. Elevated levels of SUA or hyperuricaemia have been reported to be predictors of cardiovascular diseases in non diabetic patients and those with type 2 diabetes [22
Our results on the prevalence rate of hyperuricaemia are similar to those obtained from the Melanasian Indians from Fiji [7
]. Our findings of comparable proportions of elevated SUA in both sexes may be attributable to the age of the females since the majority of them were aged greater than 50 years and likely to be menopausal. Menopausal women have been shown to have higher SUA levels than pre menopausal women and these changes are thought to result from changes in metabolism as a consequence of the menopause [24
]. Although SUA increases with aging, this increase may occur more in women especially after attainment of menopause. In a Chinese study carried out in old people, hyperuricaemia occurred more in women than in men and the increase in proportions of women with hyperuricaemia was noted more in post menopausal women (22% vs 20%) [25
]. SUA increased with age in Japanese men and women, irrespective of body mass index and alcohol consumption [26
]. In our report, the proportions of subjects with hyperuricaemia did not necessarily increase with age except for in women aged over 80 years.
We have shown in this report the clinical parameter that is likely to be contributory to the presence of hyperuricaemia is central obesity. Some researchers have however shown a possible association between SUA to BMI. Bonora et al [21
] showed a positive association between SUA and BMI in young men and Wingrove et al [24
] showed BMI to be a predictor of elevated SUA in pre but not premenopausal women.
Hyperuricaemia is reported in 25-50% of adults with hypertension [27
] and in some other reports [28
] it was found to predict the development of hypertension. In our study, we note that hypertension occurred in 54% of the study subjects with females being more affected than men. We also found the proportion of hypertensive and non hypertensive patients with hyperuricaemia was comparable and there was no association between SUA and blood pressure readings. Lu et al [25
] had similar results to ours and found no correlation between uric acid and blood pressure readings.
The MetS, a cluster of cardiovascular risk factors which include obesity, aging, sedentary lifestyle and dyslipidaemia is frequently reported in DM [30
]. The possible role of elevated SUA in the MetS is a subject that has become topical in the past few years with some studies reporting SUA to be related to the presence of the Mets [4
]. In this report, although the presence of the Mets was comparable in subjects with hyperuricaemia and those with normouricaemia, a significantly higher proportion of subjects with had hypertriglycaeridaemia and central obesity. In our correlation analysis, TG and total cholesterol were found to be positively correlated with SUA. We also found that more components of the MetS were noted in subjects with hyperuricaemia compared to those with normouricaemia. High levels of triglycerides and SUA have each been reported not only to be independently associated with an elevated risk for coronary heart disease but also show strong associations between SUA and triglyceride [5
Significant alcohol ingestion especially beer intake has been linked with elevated SUA levels and this scenario has been suggested to be likely due to the high purine content in beer [33
]. In this report, significant smoking histories were found more in subjects with hyperuricaemia than those with normouricaemia and smoking was also found to be a possible predictor of hyperuricaemia. These reports differed somewhat from those by Nikanishi et al [34
] who found that alcohol ingestion and smoking were possible determinants of the occurrence of hyperuricaemia.