Nick Mulcahy

May 07, 2016

SAN DIEGO — In patients with hyperlipidemia, statins might reduce the risk for kidney stone formation, according to a retrospective study. But, for some experts, the results are not enough to prompt the prophylactic use of the lipid-lowering drugs.

The study is timely, lead author Andrew Cohen, MD, a urologist from the University of Chicago Medical Center, said here at the American Urological Association 2016 Annual Meeting.

"The relation between levels of lipids in the blood, the intake of statins, chronic kidney disease, and kidney stones is being researched and debated currently," he told reporters during a press conference.

Elevated lipid levels have previously been associated with kidney stones. A study of 57,000 patients newly diagnosed with hyperlipidemia, showed, for the first time, that the risk for stone development was lower in statin users than nonusers (Clin Nephrol. 2013;79:351-355).

So Dr Cohen and his colleagues at the North Shore University Health System (which has more than 100 locations) decided to conduct a larger study to confirm these protective effects.

The team used the electronic medical records system to review data on more than 101,250 patients diagnosed with hyperlipidemia from 2009 to 2011 who were statin-naïve at diagnosis. The patients were followed until 2015. The primary end point of the study was the development of kidney stones.

About half (48%) the population subsequently received a statin and about half (52%) did not.

On univariate analysis, the statin users were significantly less likely to develop new stones than the nonusers (3.8% vs 4.7%; P < .01).

Multivariate analysis, adjusted for age, race, body mass index (BMI), sex, and comorbidities, confirmed the protective effect of statins on new stones (odds ratio [OR], 0.57; P < .01).

Some of the study participants had a history of kidney stones before they developed hyperlipidemia. Notably, multivariate analysis indicated that the protective effect of statins was even greater in these patients than in patients with a history of stones but no statin prescription (OR, 0.53; P < .01). The risk was "essentially cut in half," Dr Cohen reported.

The multivariate analysis was necessary because the patients who were not prescribed statins were, among other differentiators, significantly younger than nonusers (51.9 vs 60.7 years; P < .01) and less obese (28.1 vs 29.2 kg/mm²; P < .01).

Notably, on follow-up, average levels of low-density-lipoprotein cholesterol and total cholesterol were significantly lower in statin users than in nonusers, suggesting compliance with medications.

Dr Cohen stressed this finding because the earlier research on this subject lacked this analysis of lab values. This supplementary lab data added a "high degree of credibility" to our study findings, he said.

The study also confirmed other risk factors for stone development, such as being overweight, being black, being older, having osteoporosis, and having a thiazide prescription, he noted.

When the researchers looked at the relation between lipids in the blood and the risk for future kidney stones, only elevated triglyceride levels were found to be a risk factor for the development of a stone in nonusers of statins, he reported. "There was no association between elevated LDL or total cholesterol and nephrolithiasis."

The study had some limitations. When patients learned they had hyperlipidemia, they might have changed their diet or lifestyle. Plus, high cholesterol levels were often "borderline," not extremely high, Dr Cohen explained. Therefore, these results might not apply to patients with very high levels.

But the study's conclusion — that statins have a protective effect against the formation of kidney stones in adults with hyperlipidemia — will have to remain an academic matter for now, said Timothy Avench, MD, a urologist at the University of Pittsburgh, who moderated the press conference.

The results, even when combined with those from the 2013 study, are not enough to prompt a prophylactic use of statins. "It will take a lot of force to make this show up in practice," he said.

Dr Cohen has disclosed no relevant financial relationships. Dr Avench reports a financial relationship with Bard Medical.

American Urological Association (AUA) 2016 Annual Meeting: Abstract PD31-10. Presented May 8, 2016.

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