Urolithiasis mortality rate high in lower income nations

Results of a study analyzing global trends in mortality attributable to urolithiasis show that the rate declined over a recent 20-year period.

This pattern, however, was generally seen only in richer countries while lower income nations continue to suffer much higher urolithiasis-related mortality rates, reported David Bayne, MD, at the 2016 AUA annual meeting in San Diego.

“The findings of our study demonstrate the complex interplay between environment, access, and global inequality in surgery,” said Dr. Bayne, urology resident at the University of California, San Francisco.

Introducing the topic, Dr. Bayne noted that the global burden of disease is something that is not often discussed in surgery, let alone specifically in urology. Furthermore, surgical specialties are lagging behind medical specialties for reducing the global burden of disease.

“A commission on global surgery initiated by The Lancet in 2015 found that 5 billion people in the world do not have appropriate access to surgical care. In addition, it was estimated that by 2030, there would be a $21 trillion loss from global productivity without appropriate ramping up of surgical delivery,” Dr. Bayne said. He worked on the study with Anobel Odisho, MD, and co-authors.

The study investigating urolithiasis-related mortality was undertaken by urologists at the University of California, San Francisco and University of Washington, Seattle. Age-adjusted mortality rates (deaths per 100,000 people) and disease burden (Years of Life Lost, YLL and Years Lost due to Disability, YLD) for 187 countries were publically available through the University of Washington Institute for Health Metrics and Evaluation 2010 Global Burden of Disease Project for three time points (1990, 2005, 2010). Countries were classified into geographic regions and income groups based on World Bank categorizations. Information on Gross Domestic Product (GDP), Human Development Index (HDI), Gini Index, body mass index, and climate data (mean annual temperature) were obtained from World Bank, United Nations Development Programme, and World Health Organization databases.

Analysis showed that between 1990 and 2010, population-weighted global mortality from urolithiasis decreased by 27.5%, but this decrease was far greater in higher income countries relative to lower income countries. Using GDP to categorize countries into four income groups (low, lower-middle, upper-middle, and high) showed that while the mortality rate declined steadily and by more than 50% over the study period in the upper middle and high-income countries, it was essentially unchanged in the low and lower middle countries.

Next: Increased temperature linked to mortality

Increased temperature linked to mortality

A multivariate analysis conducted to identify factors independently associated with urolithiasis mortality found that increased mean annual temperature and increasing inequality (Gini Index) were associated with increasing mortality rate, while increased HDI was associated with decreased mortality. Interestingly, in the multivariate analysis, increasing GDP was associated with increasing mortality.

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Dr. Bayne noted that the opposite direction of the associations between HDI and GDP with urolithiasis mortality in the multivariate analysis suggests that although low-income countries do experience higher rates of urolithiasis mortality, unequal access to health care providers, specifically urologists, may be a more important issue in these countries rather than pure monetary factors. Furthermore, unequal access in these low income countries may encompass not just access to health care but also to resources, such as clean water.

He also observed that the validity of the mortality data from poorer countries is questionable considering the potential for less accurate recording of cause of death in those countries.

“With more accurate data in low income countries, we might see a more dramatic correlation between mortality and GDP. Or it may be that GDP is not as important as some other factors in explaining variance in mortality,” Dr. Bayne said.

The investigators noted the need for more work to better understand risk factors for urolithiasis mortality and how to minimize the global burden.

“As a next step, we will be looking at those countries that are outliers in order to determine what makes them unique and puts the population at risk for mortality from urolithiasis,” Dr. Bayne said.