Heat exhaustion behind mysterious kidney disease

In Chichigalpa, Nicaragua, almost half of all male deaths are attributable to a mysterious kidney disease. In El Salvador, it the second most common cause of death among men. In Sri Lanka, it is believed to have caused about 25 000 deaths over the past decade. Working in heat is a common factor, so the problem is expected to increase along with global warming.
The condition in question is the mysterious kidney disease CKDu, which interests a worldwide research network. Occupational health physician Kristina Jakobsson and other LU researchers are involved in the detective work.

Cane cutters work in a field that was burned the night before, covered in the black soot and ashes of the charred sugar cane in Chichigalpa, Nicaragua.

CKD means Chronic Kidney Disease. In its most prevalent form, it is a condition most common among the elderly and often associated with diabetes, excessive weight and high blood pressure.

CKDu has the same symptoms, but the “u” stands for ”unknown” as its causes are partly unidentified. This variant of the disease mainly affects agricultural workers in developing countries – young and otherwise healthy men.

“This makes the disease particularly awful. These men have provided for their families, but in the end they are too weak to work and die prematurely at the age of 45 or 50. The family has difficulty making ends meet and the children often have to drop out of school”, says Kristina Jakobsson.

Kristina Jacobsson.

She came into the field through a collaboration between LU and Managua University in Nicaragua. The collaboration started at the turn of the millennium and had been ongoing for several years when the numerous deaths among the country’s sugarcane workers started to attract attention.

“We took part in a study comparing villages in Nicaragua and El Salvador which had different main industries – sugar, coffee, fishing and so on. Medical students went out into the field with sample-gathering equipment and thousands of people were examined”, she explains.

The study showed that the sugar villages on the coast were worse affected than similar villages further inland. This indicated that the climate was an important factor. Along the coast of Central America, the climate is humid, and 35-40 degrees of heat combined with high humidity is harder on the body than dry heat.

In fact, according to international guidelines for working in heat, if you take into account the temperature, humidity, wind and solar radiation, the sugar cane workers should spend half of each working hour resting, even in the morning. They should also drink many litres of water while working, to replace lost fluids.

“Of course they are not doing that”, says Kristina Jakobsson. “Instead, they are paid on a piece rate basis, for incredibly strenuous work on fields that have been burnt before the harvest and are therefore black with soot. First they chop down the hard sugar canes with a machete, then they bend double to gather the bundles of sugar canes.”

The kidney disease among agricultural workers seems to be present in several tropical countries. Besides Central America and Sri Lanka, where it has been known for several years, similar reports are now coming from countries including India, Egypt, Thailand and Brazil. Many people believe that the disease may have been around for a long time, but that today’s industrial cultivation of sugar and rice has made the work harder, so more workers are affected.

Heat and recurrent dehydration could be the factors that trigger CKDu, Kristina Jakobsson believes. There could also be other risk factors, such as environmental toxins, infections or the painkilling drugs that the workers take to relieve pain in their back and arms.

Studies of the disease have been conducted in different ways, so they have been difficult to compare. This is why the international research network has developed a methodology for future studies in the field. The methodology includes advice on how to structure the studies, what samples to take, and a simple questionnaire.

Kristina Jakobsson now has a professorship at the University of Gothenburg, but she is on leave of absence one day a week in order to continue with her LU research. The work on CKDu was part of the Pufendorf HEAT project (see fact box), and also engages others at LU. For example, Camilla Dahlqvist, from the Division for Occupational and Environmental Medicine, has been in El Salvador to measure the muscle strain of the sugarcane workers using a method called inclinometry.

“We placed small meters on various parts of the workers’ bodies and a pulsometer around their waists. This was done before sunrise, since it was important for them to get out into the fields before it got too hot. The meters were fixed with tape and elastic bandages, so that they would stay put even when sweat began to flow”, she explains.

Unsurprisingly, the measurements showed that the strain on the sugar cane workers is among the highest ever measured throughout 25 years of mapping by occupational and environmental medics. But an experiment in which LU researchers took part showed that taking breaks in a movable tent and good access to water made the work more endurable.

These simple measures – shade, rest and water – gave the workers better kidney values and thereby reduced the risk of kidney disease. Even the owners of the sugarcane fields were satisfied: production did not decrease even though the workers took breaks and drank – on the contrary.

All the blood and urine samples from the experiment were analysed at the Division for Clinical Chemistry at LU. Its involvement started by chance.

“I happened to have the company of associate professor in clinical chemistry Magnus Abrahamson on the train from Copenhagen. Our conversation turned to the many questions around CKDu, which led to doctoral student Jenny Apelqvist getting a whole new direction to her thesis project”, explains Kristina Jakobsson.

It has not always been easy to get money for research into a disease which is so alien to our comfortable Swedish existence. But that is precisely a reason for the researchers’ engagement: that these poor agricultural workers, who struggle to provide for their families, should not need to die from the work they do.

“This really is true occupational medicine, a matter of life and death!” says Kristina Jakobsson.

She hopes that awareness of the problem will not only increase within the research community but also among those who purchase sugar from Central America and rice from Asia, for example. If the major food companies demand endurable conditions for agricultural workers, a process of change could begin. It is likely to become more urgent in future, as climate change makes conditions even hotter in the warm countries of the world.

Ingela Björck

Interdisciplinary research on heat

The research into kidney disease in agricultural workers in the tropics was part of a Pufendorf project from 2014, ”Heat”. The project gathered researchers specialising in fields such as climate modelling, water research, occupational medicine, risk management, design sciences and social sciences. The goal was to find new ways to manage the effects of increasing temperatures, as heat stress affects humans, animals and the entire ecosystem.

Several case studies were conducted within the framework of the project. They studied brick workers in India, nomads in the Himalayas, air conditioning in Hanoi and urban planning in Istanbul and Skåne. Several of the participating groups continued to work with heat issues even after the Pufendorf project ended.

EU project on working in heat

How are people who work in construction, agriculture, transport, factories and the tourism sector in Europe to deal with an increasingly warm climate? It is both a question of protecting people’s health and ensuring that productivity drops as little as possible, even when work is being done in a heatwave.

Another research project with its roots in the Pufendorf HEAT collaboration deals with this. It is the Horizon 2020 project Heat Shield, in which LU’s representative is senior lecturer and associate professor at the Department of Design Sciences Chuansi Gao. He belongs to the Thermic Environment group, which researches how heat and cold affect the human body. The EU project mainly deals with studying cold and protective clothing for agricultural workers.

Chuansi Gao is also to lead an EU collaboration project with partners from three EU countries. This will involve developing a ”climate app” which combines weather alerts with information on the heat balance in the human body, and proposes suitable measures to manage heat and cold. The app is to be adapted to the user so that the advice is different depending on factors such as the work environment, the physical strain of the work, clothing, age and health.