Mystery kidney disease linked to global warming

Washington: A mysterious kidney disease that has killed over 20,000 people in Central America and has also been observed in India and Sri Lanka may be caused by  chronic, severe dehydration linked to global climate change, a  new study has found. 

"This could be the first epidemic directly caused by  global warming," said Richard J Johnson, professor at the  University of Colorado School of Medicine in US. 

"Some districts of Nicaragua have been called the 'land  of widows' due to the high mortality rates occurring among the  male workers from chronic kidney disease," Johnson said. 

The epidemic was first described in 2002 and has been  dubbed Mesoamerican Nephropathy.  It is most prevalent among manual labourers on sugar cane  plantations in the hotter, lower altitudes of Central  America's Pacific coast. 

Theories abound about what may be causing it, including  exposure to heavy metals, pesticides and other toxic  chemicals. But Johnson believes the actual culprit is chronic  recurrent dehydration.  Researchers studied sugar cane workers in Nicaragua and  El Salvador and found that the labourers routinely worked in  conditions exceeding the recommended heat standards of the US  Occupational Safety and Health Administration (OSHA). 

Even though some of them drank up to one to two litres  per hour, the researchers found they still suffered serious  dehydration on a daily basis.  One of the major side-effects of this dehydration was  hyperuricemia or excess uric acid levels in the blood.  In one study, sugar cane workers in El Salvador had uric  acid levels of 6.6 milligrammes per decilitre in the morning  which increased to 7.2 milligrammes in the afternoon. 

Researchers also found that 21 of 23 people with chronic  kidney disease CKD had hyperuricemia.  Dehydration also activates a pathway in the kidney which  generates fructose that, when metabolised, produces uric acid.  This may contribute to the kidney damage. 

Workers who rehydrate with drinks that contain high  fructose corn syrup or sugar may be exacerbating the problem  due to the high fructose content present in the drinks.  Researchers also found that these dehydrated workers had  high concentrations of uric acid crystals in their urine. 

This 'sandy urine' is associated with signs of  dehydration, including light headedness, elevated heart rates  and headache. The uric acid crystals are thought to trigger  tubular damage and fibrosis in the kidneys. 

The study suggests that this epidemic may be gaining  momentum now because global warming is increasing the risk of  dehydration. 

"Temperatures have been progressively increasing in El  Salvador over the last century, with an average increase of  0.5 degrees Celsius since 1980," the study said. 

Johnson said that this kind of CKD is now being observed  in Sri Lanka, India, Thailand, and Egypt.  The study was published in the American Journal of Kidney  Diseases.