Abstract
BackgroundIn Japan, the incidence of kidney stones has increased markedly in recent decades. Major causes of kidney stones remain unclear, and limited data are available on the relationship between overweight/obesity and the incidence of kidney stones. We therefore evaluated body mass index (BMI) and the incidence of kidney stones in Japanese men.MethodsOf the workers at a gas company, 5984 males aged 20–40 years underwent a medical examination in 1985 (baseline). This study includes 4074 of the men, who were free of kidney stones at baseline and underwent a second medical examination performed between April 2004 and March 2005. BMI was calculated from measured height and weight in 1985, and men were categorized into tertiles. The development of kidney stones during follow-up was based on self-reports from questionnaires at the second medical examination.ResultsThe average duration of follow-up was 19 years, with 258 participants developing kidney stones during this period. Using the lowest BMI (1st tertile) group as a reference, the hazard ratios (95% confidence intervals [CIs]) for the 2nd and 3rd BMI tertiles were: 1.26 (95% CI, 0.92–1.73) and 1.44 (95% CI, 1.06–1.96), respectively (P for trend = 0.019). After additionally adjusting for potential confounders, such as age, systolic blood pressure, cardiorespiratory fitness, cigarette smoking, and alcohol consumption, the hazard ratios were 1.28 (95% CI, 0.93–1.76) and 1.41 (95% CI, 1.02–1.97), respectively (P for trend = 0.041).ConclusionsThese results suggest that increased BMI is a risk factor for kidney stones in Japanese men.
Highlights
Kidney stones are one of the most common urological disorders in Japan
Those who did not undergo the exercise test for measurement of cardiorespiratory fitness as an objective marker of physical fitness in 1985 and those who reported that they had a history of kidney stones before 1985 on medical examinations performed between April 2004 and March 2005, which was the last year of the follow-up, were excluded (n = 1575), leaving 4074 males for the present study
Participants with lower body mass index (BMI) tended to be younger and have lower blood pressure, while cardiorespiratory fitness tended to be higher in the low BMI group
Summary
Kidney stones are one of the most common urological disorders in Japan. According to the Japanese urolithiasis clinical guidelines, the ratio of occurrence of upper (kidney and ureteral) and lower (bladder and urethral) urinary tract stones has been mostly stable in recent years, with upper urinary tract stones accounting for about 96% of all cases of urolithiasis.[1]. Regarding the incidence of kidney stones in Japan, upper urinary tract stone occurrence has increased markedly in recent decades.[2] The age-adjusted annual incidence of upper urinary tract stones in 2005 was 165 per 100 000, which was more than double the incidence in 1965 (81 per 100 000).[2] The lifetime incidence of kidney stones is not low: 15.3% in males and. In Japan, the incidence of kidney stones has increased markedly in recent decades. We evaluated body mass index (BMI) and the incidence of kidney stones in Japanese men. This study includes 4074 of the men, who were free of kidney stones at baseline and underwent a second medical examination performed between April 2004 and March 2005. Conclusions: These results suggest that increased BMI is a risk factor for kidney stones in Japanese men
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