TRENTON, N.J. — Getting married, divorced, demoted or sued could hurt more than your wallet. Such changes also may trigger kidney stones, according to a study that, for the first time, links the painful ailment with stress.
The study, comparing 200 kidney-stone patients with 200 similar people without the affliction, found the patients were more likely to have endured major stress in the previous two years, said lead researcher Dr. G. Reza Najem of the University of Medicine and Dentistry of New Jersey.
Those stresses included both positive events, such as marriage or birth of a child, and negative events, such as financial problems or death of a loved one. The study was published in the October issue of the International Journal of Epidemiology.
"The people who have kidney stones, they have significantly more incidents of stress," said Najem, a professor of preventive medicine and community health at the UMDNJ-New Jersey Medical School in Newark.
If others confirm his findings, Najem said, it could lead to increased focus on stress management to prevent recurrences of kidney stones.
Kidney stones occur when excess calcium and other substances crystallize in ducts connecting the kidneys and bladder, causing pain from the blockage of urine or the sharp edges scraping the ureter as the stone passes through.
About 12% of Americans develop a kidney stone at some point, and each has a 50% chance of recurrence within 10 years and an 80% chance of eventual recurrence.
Kidney stones cost about $1.7 billion annually for medical treatment consisting generally of medication, removal of the stone through a tiny device threaded up the urethra and bladder, or the increasingly popular and less painful use of shock waves to break the stones into tiny pieces.
Najem said the study is important because scientists do not agree on what causes kidney stones, although there are numerous theories and likely risk factors, such as excessive calcium or protein consumption and insufficient fluid intake.
"If it's not diet, it's not calcium, it's not protein, what is it?" Najem wondered, leading him to test his hypothesis that stress was involved.
Najem found that the subjects with kidney stones reported experiencing a combined 1,428 stressful events the previous two years, compared with 1,177 stressful events for the control subjects--although the control subjects were relatives and friends of the patients and thus, he said, likely to have faced the same problems.
Of the 60 stressors about which participants were questioned, those with kidney stones were at least 1.5 times more likely to report 18 of them. For instance, patients were 3.5 times more likely than non-patients to report loss of contact or bad relationships with a child, 3.1 times more likely to have had mortgage problems and 2.6 times more likely to have experienced stress of pregnancy during the previous two years.
The patients, who were treated at the Stone Center of New Jersey in Newark, also were much more likely to have unexplained health problems and activity limitations due to health problems.
Two kidney-stone experts called the study a good start in an area of limited knowledge. However, they said, its conclusions are weakened by having used relatives and friends accompanying the patients as the controls and relying on subjects' memories of their diet, problems and other items for the previous two years.
Stronger proof would come from studying thousands of healthy people, checking their stress levels periodically over a few years, and seeing which ones eventually developed kidney stones, although that would be enormously expensive and complicated, said Dr. Alan Wasserstein, director of the stone evaluation center at the Hospital of the University of Pennsylvania in Philadelphia.
Besides medication, prevention steps include drinking 10 glasses of water daily, increasing fiber in the diet and reducing consumption of salt, refined sugars, protein and possibly calcium.