Income is strongly associated with kidney stone disease-specific quality of life

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INTRODUCTION

Kidney stones are a source of significant morbidity and have been shown to negatively impact health-related quality of life (HRQOL). While socioeconomic status (SES) is associated with HRQOL, it has never been examined in relation to kidney stone disease-specific HRQOL. The purpose of this study was to assess kidney stone patients’ quality of life in relation to income.

METHODS

This was a multi-institutional prospective cohort study where kidney stone patients at 10 stone centers across the U.S. were enrolled. They completed the Wisconsin Stone Quality of Life questionnaire (WISQOL – a validated HRQOL questionnaire specifically tailored to kidney stone patients) between June 2014 and March 2017 at the time of their first clinic visit when presenting for initial stone evaluation. Race/ethnicity was defined by self-report. Each patient’s income was estimated using census median incomes identified by zip code, then further classified into low, middle, and upper income brackets using Pew Research Center guidelines. Linear regression was used to examine the relationship between income and HRQOL, adjusting for age, gender, race, BMI, number of stone events, and number of comorbidities.

RESULTS

The study sample included 1,777 individuals. Older age and male gender were significantly associated with higher WISQOL scores (p<0.010). Factors associated with lower WISQOL scores were low income, non-White race, overweight or extremely obese BMI, the presence of 3 or more comorbidities, and severe recurrent stone formation. In a multiple regression model, the effect of income on QOL weakened but remained statistically significant (p<0.050, Table 1).</p>

CONCLUSION

Lower income, when adjusted for age, race, gender, BMI, number of stone events, and comorbidities, is statistically significantly associated with lower stone-specific HRQOL. Understanding how SES impacts HRQOL may lend insight into ways to optimize the management of patients with kidney stones.

Funding: NIH grant P20-DK-116