Abstract
Introduction:Large variations in demographic, economic and environmental factors might influence the worldwide distribution of urolithiasis, but scarce data are available concerning their associations with stone composition. We aimed to evaluate the frequency and composition of kidney stones and their associations with temperature, humidity, and human development index (HDI).Materials and Methods:A total of 1,158 stones from distinct patients (47±14 years old, male/female 2:1) were included. The mean annual temperature and relative humidity of each town were considered separately.Results:Calcium oxalate monohydrate (COM) was disclosed in 38.8% of patients, calcium oxalate dihydrate (COD) in 22.1%, mixed COD/apatite in 9.4%, pure apatite in 1.9%, brushite in 1.8%, struvite in 8.3%, pure uric acid in 11.1%, mixed uric acid/COM in 5.6%, and cystine/rare types in 0.8%. Mean HDI of all pooled cities was 0.780±0.03. However, people living in HDI<0.800 regions had twice the odds of having a struvite stone versus those living in HDI>0.800 (OR=2.14, 95% CI 1.11-4.11). Furthermore, a progressive increase in the struvite stones frequency from 4.5 to 22.8% was detected from HDI>0.800 through HDI<0.700. No significant difference for other stone types was disclosed. Separate logistic regression models assessed the association of each stone composition with gender, temperature, humidity and HDI as covariates.Conclusion:Patients living in low HDI areas are more prone to develop struvite stones, possibly due to lower access to healthcare. Temperature and humidity did not represent a specific risk factor for any stone type in the present sample.
Highlights
Large variations in demographic, economic and environmental factors might influence the worldwide distribution of urolithiasis, but scarce data are available concerning their associations with stone composition
The distribution of stone types and ages was as follwos: calcium oxalate monohydrate (COM) in 38.8% of patients (49±13 y/o), calcium oxalate dihydrate (COD) in 22.1% (43±14 y/o), mixed COD/apatite in 9.4% (44±14 y/o), pure apatite in 1.9% (46±15 y/o), struvite in 8.3% (44±14 y/o), brushite in 1.8% (41±12 y/o), pure uric acid in 11.1% (54±12 y/o), and mixed uric acid/Calcium oxalate monohydrate (COM) stones in 5.6% (54±13 y/o)
The mean age was significantly higher only in the two groups containing uric acid as the major component compared to all other groups (p
Summary
Economic and environmental factors might influence the worldwide distribution of urolithiasis, but scarce data are available concerning their associations with stone composition. In the United States, it has markedly changed, almost doubling the prevalence during the last twenty years from 5 to 9%4,5 The reasons for this increase are still unclear, but changes in dietary habits affecting both urinary biochemical parameters and stone composition could represent causal factors[6,7]. To support this information, recent epidemiological data by Ferraro et al.[8] examining cohorts including mostly calcium stone formers revealed that body mass index (BMI), sugar sweetened beverage intake, lower fluid intake, DASH (Dietary Approaches to Stop Hypertension) as well as calcium intake represented the most important modifiable factors for kidney stone prevention. Several other factors may be involved in the formation of kidney stones
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