The relationships between smoking and levels of serum urea and uric acid. Results of an epidemiological survey

Association between smoking and gout: a meta-analysis

Previous studies showed that smoking is linked with the decreased risk of gout, but the results remain controversial. The aim of this meta-analysis was to determine the associations between smoking and the risk of gout. A systematic literature search of PubMed and EMBASE was conducted. Data were extracted by two independent reviewers. The pooled odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of associations, using random effects and fixed effects models. Five studies with a total of 17,915,507 participants with 16,880 gouts were enrolled. Heterogeneity among the effect sizes of five studies was reported as I² = 87.9%. Our meta-analysis indicated that smoking (ever- vs non-, OR = 0.87, 95% CI = 0.67-1.12) was not associated with the risk of gout in random effects model, whereas there was an association between smoking (ever- vs non-, OR = 0.70, 95% CI = 0.65-0.74) and gout risk in fixed effects model. Our finding indicates that smoking may not be involved in the risk of gout. However, further studies are still needed to confirm our results.

An association of smoking with serum urate and gout: A health paradox

BACKGROUND

The potential effect of cigarette smoking on levels of serum urate and risk of gout has been considered by a large number of studies, either as the primary variable of interest or as a covariate.

METHODS

Here we systematically review the published evidence relating to the relationship of smoking with serum urate, hyperuricaemia, and gout.

RESULTS

Many studies have reported that smoking reduces serum urate, however, the evidence has not been conclusive with other studies pointing to the opposite or no effect. It has also been suggested that smoking reduces the risk of gout, although there is some evidence to contradict this finding.

CONCLUSION

A consensus has yet to be reached as to the effect of smoking on serum urate levels and the risk of gout.

Cigarette Smoking and the Risk of Incident Gout in a Prospective Cohort Study

OBJECTIVE

Cigarette smoking is shown to reduce serum urate. However, its impact on risk of gout is unknown. We prospectively examined the relationship between cigarette smoking and gout risk in this Asian cohort.

METHODS

We analyzed the data from the Singapore Chinese Health Study, a cohort of 63,257 Chinese ages 45-74 years at recruitment in 1993-1998. Information on cigarette smoking and other lifestyle factors was collected through in-person interviews at recruitment. This analysis included 53,213 participants who took part in either the first followup (1999-2004) and/or the second followup interviews (2006-2010). Cox proportional hazards models were used to assess the relationship between cigarette smoking and gout risk.

RESULTS

A total of 2,244 incident cases of physician-diagnosed gout were identified after a mean followup of 11.1 years. Among men, compared to never smokers, the risk of gout in current smokers was decreased by 27% (hazard ratio [HR] 0.73 [95% confidence interval (95% CI) 0.63-0.84]). This risk reduction was greater in lean male smokers (HR 0.69 [95% CI 0.57-0.83]) than overweight smokers (HR 0.87 [95% CI 0.67-1.13]) (P = 0.09 for interaction). This inverse association with smoking was rapidly attenuated to become null even in former smokers who had recently quit smoking. Conversely, there was no association between smoking and gout risk in women. In a companion cross-sectional study, current smokers had significantly lower levels of serum urate than former and never smokers, and this observation was present in men and not women.

CONCLUSION

Current smoking is associated with lower risk of gout in men in this Asian cohort.

Prevalence and determinants of hyperuricemia in middle-aged, urban Chinese men

BACKGROUND

Hyperuricemia is associated with metabolic syndrome and has emerged as a marker for both type 2 diabetes and cardiovascular disease. We estimated the prevalence and lifestyle risk factors of hyperuricemia in middle-aged, urban Chinese men.

METHODS

The study included 3,978 urban Chinese men 40-74 years of age from a population-based cohort study, the Shanghai Men's Health Study, who were free of type 2 diabetes at baseline and had provided fasting blood samples. Uric acid concentrations were measured by the uricase method. Hyperuricemia was defined as >7.0 mg/dL. Anthropometric measurements and information on lifestyle factors and disease history were collected by in-person interviews.

RESULTS

One quarter of the study subjects had hyperuricemia. Participants with metabolic syndrome had a higher prevalence of hyperuricemia. Body mass index (BMI), waist-to-hip ratio (WHR), waist circumference, and weight gain (since age 20) were positively associated with the prevalence of hyperuricemia. Physical activity was inversely related to the prevalence of hyperuricemia. The odds ratios for hyperuricemia for quintiles of nonoccupational physical activity were 1.00, 0.80, 0.73, 0.75, and 0.57 (P trend <0.001). Participants with hyperuricemia were less likely to be current smokers, but were more likely to drink alcohol regularly. Beer consumption was associated with higher risk of hyperuricemia compared with consumption of wine or liquor.

CONCLUSIONS

In this representative sample of middle-aged, urban Chinese men, hyperuricemia is highly prevalent. Obesity, weight gain in adulthood, and alcohol intake were associated with a higher prevalence of hyperuricemia, whereas daily physical activity and smoking were inversely related to the prevalence of hyperuricemia.

A longitudinal study of the influence of shift work on serum uric acid levels in workers at a telecommunications company

BACKGROUND

Hyperuricemia is a lifestyle-related disease. Although there have been many previous reports about the association of serum uric acid (UA) levels with lifestyle, including eating habits and alcohol intake, there has been no report of a longitudinal study of the relationship between serum UA levels and shift work.

AIMS

To clarify the influence of shift work on serum UA levels in Japanese workers.

METHODS

This was a 4-year cohort study of 15 871 workers at a telecommunications company. Pooled logistic regression analyses by sex were performed, with job schedule type, age, body mass index (BMI), lifestyle and the results of blood chemistries as covariates.

RESULTS

In males, shift work, part-time work, BMI, consumption of alcohol (less than twice per week, two to five times per week or more than five times per week) and little preference for vegetables were positively associated with the development of increased serum UA (>or=8 mg/dl in males, >or=6 mg/dl in females). In females, age, BMI and a history of smoking were positively associated with the development of increased serum UA.

CONCLUSION

This study revealed that shift work is independently related to increased serum UA in males.

Relations of hyperuricemia with the various components of the insulin resistance syndrome in young black and white adults: the CARDIA study. Coronary Artery Risk Development in Young Adults

PURPOSE

To assess the association of hyperuricemia with the various components of the Insulin Resistance Syndrome (IRS) in a biracial cohort of young adults.

METHODS

Cross-sectional study in 4053 young black and white adults aged 18-30 years from the Coronary Artery Risk Development in Young Adults (CARDIA) study.

RESULTS

Body mass index (BMI), fasting insulin, and triglycerides were significantly higher, and high density lipoprotein (HDL)-cholesterol lower in subjects with hyperuricemia (uric acid > or = 7.0 mg/dl in males; > or = 6.0 mg/dl in females) (all p < 0.001). BMI showed the strongest positive correlation with uric acid among the IRS components. Significant associations of hyperuricemia with these risk factors were observed in all sex-race groups, which persisted after controlling for possible confounders including age, education, physical activity, smoking, alcohol intake, oral contraceptive use, and creatinine. Further adjustment for BMI and/or waist-to-hip ratio caused a large decrease in the strength of the associations. Adjustment for insulin also lead to decreases; however, the influence of fasting insulin appeared weaker than obesity. Even after controlling for obesity, insulin, and the other components of the IRS, male subjects in both races in the upper tertile of triglycerides were still more likely to have hyperuricemia.

CONCLUSIONS

The association of hyperuricemia with most aspects of the IRS may result predominantly from their covariation with adiposity and secondarily with insulin level. Elevated triglyceride level seems to have an independent relationship with hyperuricemia in males. The relationship between hyperuricemia and cardiovascular disease observed in previous studies may be secondary to its association with the IRS.

Uric acid, xanthine oxidase and other risk factors of hypertension in normotensive subjects

Uric acid produced by xanthine oxidase (also a source of superoxide radicals) has been known to increase in hypertensive patients. In this study we evaluated the possible involvement of uric acid and xanthine oxidase in the pathogenesis of hypertension by examining their association with mean arterial pressure (MAP) and factors related to blood pressure. These factors include age, quetelet index (weight/height2), cholesterol, creatinine, calcium (Ca), magnesium (Mg), sodium (Na), potassium (K) and urea. Fifty Two (male-19, female-33) normal healthy individuals were studied. Correlation studies of demographic variables showed that age was positively correlated with MAP [r = 0.309, p = 0.026] and cholesterol [r = 0.503, p = 0.000] while quetelet index was positively correlated with age [r = 422, p = 0.000] MAP [r = 0.331, p = 0.016] and xanthine oxidase [r = 0.331, p = 0.016]. MAP was positively correlated with uric acid [r = 0.511, p = 0.000], cholesterol [r = 0.492, p = 0.000] and xanthine oxidase enzyme activity [r = 0.388, p = 0.004] and negatively correlated with plasma calcium [r = 0.603, p = 0.000]. Correlation studies of measured parameters with uric acid and xanthine oxidase showed that uric acid was positively correlated with creatinine [r = 0.627, p = 0.000], plasma magnesium [r 0.442, p = 0.001] and negatively correlated with plasma calcium [r = 0.546, p = 0.000] while xanthine oxidase was negatively correlated with plasma calcium [r = -0.404, p = 0.003] and plasma sodium [r = -0.288, p = 0.038]. Stepwise multiple regression with MAP as dependent variable showed that 65% of total variability of blood pressure can be accounted for by plasma calcium, cholesterol, creatinine, plasma K, plasma Na, uric acid and xanthine oxidase in order of increasing R2 [xanthine oxidase: T-value = 3.26, R2 = 0.653]. It can be concluded that in normotensive subjects, uric acid and xanthine oxidase have significant association with blood pressure and thus are one of the many factors which are involved in the cause or effect of hypertension.