Gout and hyperuricemia in a Finnish rural population

Gout: global epidemiology, risk factors, comorbidities and complications: a narrative review

BACKGROUND

Gout is one of the oldest known diseases and the most common form of inflammatory arthritis. The established risk factors for gout include hyperuricemia, chronic renal disease, genetic, alcohol consumption, dietary factors, diuretic use, hypertension, obesity, and metabolic syndrome. Patients with gout have an increased risk of all-cause mortality, particularly from cardiovascular disease, cancer, and infectious diseases. Gout is also associated with several complications, such as nephrolithiasis. This literature review describes the global epidemiology and trends associated with gout, before providing an overview of its risk factors and complications.

METHODS

This research used the narrative review method. Thorough searches were performed in PubMed and Google scholar, up to June 15, 2024, for articles that evaluated the risk factors, comorbidities or complications associated with gout. Moreover, we also included studies that reported the epidemiological characteristics or burden of gout at the global, regional, or national level.

RESULTS

Gout is more prevalent in developed countries, than in developing countries, although its prevalence is increasing globally. In addition, gout is much more prevalent among males than among females. Hyperuricemia has the largest role in the development of gout, although many risk factors contribute to the increasing prevalence of gout, including genes, several medications, and diet. Gout is associated with several comorbidities and complications, which need to be taken into consideration when managing gout. In recent years, gout has been found to be associated with several new comorbidities.

CONCLUSIONS

Our findings provide a comprehensive and informative overview that can be useful for the prevention, diagnosis, and management of gout.

Reference range of serum uric acid and prevalence of hyperuricemia: a cross-sectional study from baseline data of ELSA-Brasil cohort

Background

Most of the few studies that have established reference ranges for serum uric acid (SUA) have not taken into account factors which may interfere with its levels and followed rigorous laboratory quality standards. The aim of this study was to establish reference ranges for SUA and determine the prevalence of hyperuricemia.

Method

Cross-sectional study including 15,100 participants (all sample) aged 35 to 74 years from baseline data of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), a multicentric cohort of volunteer civil servants from five universities and one research institute located in different regions of Brazil. It was established a reference sample excluding participants with factors that directly influence SUA levels: glomerular filtration rate lower than 60 ml/min, excessive alcohol intake, use of diuretics, aspirin, estrogen or urate-lowering therapy. SUA was measured using the uricase method and following rigorous international quality standards. Reference ranges were defined as values between percentiles 2.5 (P2.5) and 97.5 (P97.5) of SUA distribution in the reference sample, stratified by sex. Hyperuricemia was defined as SUA ≥ 7 mg/100 ml in the all sample.

Results

The reference sample was composed of 10,340 individuals (55.3% women, median age 50 years). Reference ranges (P2.5 to P97.5) for SUA were: 4.0 to 9.2 mg/100 ml for men and 2.8 to 6.9 mg/100 ml for women. Sex was a major determinant for SUA levels (median [IQR], mg/100 ml: 6.1 [5.3–7.0] for men versus 4.5 [3.9–5.3] for women, p < 0.001). Higher levels of SUA were found in patients with higher BMI. Higher age had (a modest) influence only for women. The prevalence of hyperuricemia for all sample (N = 15,100) was 31.9% (95% confidence interval [CI] 30.8–33.0%) in men and 4.8% (95% CI 4.3–5.3%) in women.

Conclusion

SUA reference ranges were 4.0 to 9.2 mg/100 ml for men and 2.8 to 6.9 mg/100 ml for women. Prevalence of hyperuricemia was 31.9% in men and 4.8% in women. Updated SUA reference ranges and prevalence of hyperuricemia are higher nowadays and might be used to guide laboratories and the screening for diseases related to SUA.

The Relationship between Alcohol Consumption and Gout: A Mendelian Randomization Study

Gout is a disease that manifests itself after decades of following a high-purine diet, with excessive alcohol consumption assumed to be one of the main contributors to the development of the disease. This study performs a Mendelian randomization (MR) analysis to determine whether alcohol consumption causally affects the risk of developing both hyperuricemia and gout. The results indicate that genetically predicted drinks consumed per week have no causal effect on neither the risk of gout (p = 0.35), nor serum uric acid levels (p = 0.73). For MR analysis in the other direction, genetic risk of gout was significantly associated with drinks per week (p = 0.03). Furthermore, the results of the MR analysis were verified in a cohort of individuals diagnosed with hyperuricemia and gout, comprising of alcohol-consuming and alcohol-abstaining subgroups. When split by alcohol status, the serum uric acid levels failed to show a significant difference in both gout (p = 0.92) and hyperuricemia (p = 0.23) subgroups. Overall, the results suggest that increased alcohol consumption does not play a causal role in the development of gout.

Wastewater-based estimation of the prevalence of gout in Australia

Allopurinol, a first-line gout treatment drug in Australia, was assessed as a wastewater-based epidemiology biomarker of gout via quantification of the urinary metabolite, oxypurinol in wastewater. The in-sewer stability of oxypurinol was examined using laboratory-scale sewer reactors. Wastewater from 75 wastewater treatment plants across Australia, covering approximately 52% (12.2 million) of the country's population, was collected on the 2016 census day. Oxypurinol was quantified in the wastewater samples and population-weighted mass loads calculated. Pearson and Spearman rank-order correlations were applied to investigate any link between allopurinol, other selected wastewater biomarkers, and socio-economic indicators. Oxypurinol was shown to be stable in sewer conditions and suitable as a WBE biomarker. Oxypurinol was detected in all wastewater samples. The estimated consumption of allopurinol ranged from 1.9 to 32 g/day/1000 people equating to 4.8 to 80 DDD/day/1000 people. The prevalence of gout across all tested sewer catchments was between 0.5% to 8%, with a median of 2.9% nationally. No significant positive correlation was observed between allopurinol consumption and alcohol consumption, mean age of catchment population, remoteness or higher socioeconomic status. There was a significant positive correlation with selective analgesic drug use. Wastewater analysis can be used to study gout prevalence and can provide additional insights on population level risk factors when triangulated with other biomarkers.

Global epidemiology of gout: prevalence, incidence and risk factors

Gout is a crystal-deposition disease that results from chronic elevation of uric acid levels above the saturation point for monosodium urate (MSU) crystal formation. Initial presentation is mainly severely painful episodes of peripheral joint synovitis (acute self-limiting 'attacks') but joint damage and deformity, chronic usage-related pain and subcutaneous tophus deposition can eventually develop. The global burden of gout is substantial and seems to be increasing in many parts of the world over the past 50 years. However, methodological differences impair the comparison of gout epidemiology between countries. In this comprehensive Review, data from epidemiological studies from diverse regions of the world are synthesized to depict the geographic variation in gout prevalence and incidence. Key advances in the understanding of factors associated with increased risk of gout are also summarized. The collected data indicate that the distribution of gout is uneven across the globe, with prevalence being highest in Pacific countries. Developed countries tend to have a higher burden of gout than developing countries, and seem to have increasing prevalence and incidence of the disease. Some ethnic groups are particularly susceptible to gout, supporting the importance of genetic predisposition. Socioeconomic and dietary factors, as well as comorbidities and medications that can influence uric acid levels and/or facilitate MSU crystal formation, are also important in determining the risk of developing clinically evident gout.

Hyperuricemia as a risk factor for cardiovascular mortality

The value of hyperuricemia as a risk factor for cardiovascular mortality was investigated in 3195 men and 3160 women aged 40-69 years in Finland. Hyperuricemia was associated with obesity, impaired glucose tolerance, hypertension and history of heart disease. The total mortality of hyperuricemic men and women in 5 years was significantly higher than the mortality of normouricemics. Cardiovascular mortality was not higher in hyperuricemics than in normouricemics. However, in hyperuricemic women without known heart disease cardiovascular mortality was significantly increased in the follow-up period between 5 and 12 years. Total and cardiovascular mortality rates were significantly higher in hyperuricemic men with known heart disease than in corresponding normouricemic men. A rise of serum uric acid may be secondary to more advanced atherosclerosis. Thus, hyperuricemia may be associated with more advanced heart disease and it is not an independent cause of cardiovascular diseases.

Diuretics and hyperuricemia in the elderly

Serum uric acid (SUA) was studied in a rural population of 420 males and 592 females aged 65 years or more. The mean SUA concentration was 0.313 mmol/l in males and 0.316 mmol/l in females. In males, 47 (11.2%) and in females 60 (10.1%) had a SUA level of 0.42 mmol/l or more. Both the mean serum values and the frequency of hyperuricemia were higher than 11 years earlier in another, similar study. The SUA concentration was 0.361 mmol/l in the 435 individuals using diuretics and 0.281 mmol/l in the remaining 578. Of the 107 hyperuricemic individuals, 82% used diuretics, and only 2 out of those 20 where the SUA level was 0.50 mmol/l or more did not use diuretics. Apart from diuretics, only the serum creatinine concentration, the Body Mass Index, body weight and the hematocrit level were significantly associated with hyperuricemia in both sexes.

Serum uric acid levels among thirty-four thousand people in Japan

During 1978 a survey was carried out on 34 036 people in Nagano Prefecture, Japan, in an epidemiological study of hyperuricaemia; 15 713 males and 18 324 females were examined by means of our health examination car. The subjects of the survey were all volunteers. The results have shown that the serum uric acid (SUA) levels were related to sex and age. The male group had a mean SUA level of 5.82 mg/dl (range 0.9 to 11.8 mg/dl, standard deviation 1.14 mg/dl) (0.35, range 0.05-0.7, SD 0.07 mmol/l), and the female group had a mean of 4.33 mg/dl (range 0.5 to 9.7 mg/dl, standard deviation 0.91 mg/dl) (0.26, range 0.03-0.58, SD 0.05 mmol/l). The distribution curve for SUA was almost normal in both sexes. Lower levels of SUA were found in males from the 2nd to the 6th decade, but they increased again after the 7th decade. In females they gradually decreased and were at the lowest in the 4th and 5th decades, and then increased again. The values were always lower in females than males with the difference ranging from 1.84 to 0.81 mg/dl (0.11-0.05 mmol/l).

Serum uric acid in England and Scotland

Serum uric acid (SUA) was measured in 512 men and 254 women from two English regions and in 337 men from one Scottish region. Mean SUA levels were the same in the men (5-5 mg/100 ml) and similar in the women (3-9 and 4-1 mg/100 ml). The apparent rarity of gout in Scotsmen cannot be explained by regional differences in SUA levels or in the prevalence of hyperuricaemia (defined as SUA of 7-0 mg/100 ml or over) which was present in 6-6% of the English men and 8% of the Scots. SUA was positively correlated with weight and serum urea, and with age in women, but no variation was found with social class. Body weight was the most important predictor of SUA in both men and women and superior to measurements involving correction for height, such as ponderal index and calculated lean body mass.

Gout, particularly diuretics-induced, is one the increase in Finland

Gout has been considered a rare disease in Finland. However, our hospital series of 77 patients from 1952 to 1976 shows a striking increase during the last 8 years. Over those 8 years the number of persons in the whole country receiving prescribed reimbursable medicines for gout and/or hyperuricaemia rose 10-fold, from 218 to 2188. Diuretics were implicated in one-fourth of our patients-all recent cases. Associated morbidity was high in both obese and non-obese patients. The clinical features and dietary habits of the patients are discussed.

Serum uric acid levels in England and Scotland

A survey of serum uric acid levels in 766 subjects in England and 337 in Glasgow was carried out. There was no difference in the frequency distribution of uric acid or the mean levels in the two countries. A serum uric acid of 7 mg/100 ml or over was found in 7.2% of the men and 0.4% of the women. The previously described sex difference and association of serum uric acid with weight were confirmed. No association was found with social class. The suggestion of an increase in uric acid levels in the United Kingdom over the past 14 years is discussed.

A multi-disciplinary catalogue of uric acid literature of interest to behavioural scientists

The research on uric acid encompasses a large number of disciplines and their respective journals. This bibliography (1948 to 1972) was assembled to provide a co-ordinated reference to this source material for behavioural scientists.