[Obesity as risk factor for lithiasic recurrence]

Comorbidity and socio-demographic factors associated with renal lithiasis in persons aged 40 to 65: A cross-sectional study

BACKGROUND AND OBJECTIVE

Renal lithiasis is one of the most important urological diseases. It seems to be related to different socio-demographic and climatic factors, lifestyle and pre-existing comorbidity. The aim of this study was to examine the relationship between socio-demographic variables, certain risk factors and chronic diseases and the renal lithiasis.

PATIENTS AND METHOD

A cross-sectional population-based study was carried out, selecting the Spanish population aged from 40 to 65 years, combining 2 random samples (PreLiRenA and PreLiRenE studies). Data were collected by personal telephone surveys, gathering information on socio-demographic variables and perceived morbidity. Data on annual average temperatures in each Spanish region were also collected. A bivariate and multivariate analysis was performed.

RESULTS

A total of 4,894 subjects were surveyed; 51.3% were women; 25% were aged 40-45 years, 36% had primary school education and 31.4% were of low social class. The overall prevalence of renal lithiasis was 15.0% (95% confidence interval [95% CI] 14.5-15.5). By means of multivariate analysis, the variables that showed a strong statistical relationship with the presence of renal lithiasis were: older age (61-65 years; OR=1.39; 95% CI 1.06-1.80), high social class (OR=1.98; 95% CI 1.29-2.62), family history of renal lithiasis (OR=2.22; 95% CI 1.88-2.65), high blood pressure (OR=1.68; 95% CI 1.39-2.02) and overweight/obesity (OR=1.31; 95% CI 1.12-1.54). A correlation was observed between renal lithiasis and average annual temperatures in the Spanish regions (r=0.59; P=.013).

CONCLUSIONS

A relationship was observed between renal lithiasis and older age, belonging to higher social classes, the existence of a family history of urolithiasis, and hypertension and overweight or obesity. The prevalence of renal lithiasis is greater in warmer climate zones.

Obesity and urolithiasis: evidence of regional influences

There is evidence that obese patients have an increased risk of renal stone formation, although this relationship could be less evident in some populations. The aim of this study was to evaluate the impact of overweight and obesity on the risk of renal stone formation in a population consuming a Mediterranean diet and to better elucidate the mechanisms underlying the increased risk of urolithiasis observed in obese subjects. We performed a retrospective review of 1698 stone forming patients (mean age 45.9 ± 14.6 years; 984/714 M/F), attending outpatient stone clinics in Milan and Florence, seen between January 1986 and June 2014. Records were reviewed and data collected pertaining to age, gender, weight, height, stone composition, association with diabetes type 2 or gout and metabolic profile of 24-h urine to perform a descriptive study. We estimated prevalence ratios for body mass index (BMI) categories (underweight: BMI <18.5, normal: BMI 18.5-24.9, overweight: BMI 25-29.9 and obese ≥30). Overweight and obesity were present in 40.7 and 8 % of the men and in 19.9 and 8.7 % of the women in the study population. The mean BMI of patients with urolithiasis was found to be 24.5 ± 7.5 kg/m². BMI values were positively correlated with age (p = 0.000) and mean BMI was higher in males than in females (25.5 ± 8.9 vs 23.2 ± 4.4 kg/m²). In males, rates of overweight and obesity in renal stone formers were higher than the rates reported in the Italian general population in 2004 only for the age group 25-44 years, whereas males in all the other age groups and in females the rates of overweight and obesity in renal stone formers were similar to rates reported in the Italian general population. The rates of overweight and obesity were significantly different in patients with different chemical stone composition. In particular, patients with uric acid stones have rates of overweight and obesity higher than patients with calcium stones or other types of calculi. Also the rates of type 2 diabetes and gout were greater in patients with overweight and obesity. In overweight and obese patients, the urinary excretion of risk factors for stone formation, such as calcium, oxalate and urate, and also of inhibitory substances, such as citrate, were significantly higher than in patients with normal weight or underweight. The prevalence of overweight and obesity in patients with urinary calculi from a country consuming a Mediterranean diet is not higher than in the general population. It should be taken into account that not all the dietary patterns that are associated with obesity may involve a parallel increase in the risk of forming kidney stones and that epidemiological findings from one country could not be confirmed in other countries with different climatic, socioeconomic and cultural features.