Climate Trends at a Hotspot of Chronic Kidney Disease of Unknown Causes in Nicaragua, 1973-2014

Abstract

An ongoing epidemic of chronic kidney disease of uncertain etiology (CKDu) afflicts large parts of Central America and is hypothesized to be linked to heat stress at work. Mortality rates from CKDu appear to have increased dramatically since the 1970s. To explore this relationship, we assessed trends in maximum and minimum temperatures during harvest months between 1973 and 2014 as well as in the number of days during the harvest season for which the maximum temperature surpassed 35 °C. Data were collected at a weather station at a Nicaraguan sugar company where large numbers of workers have been affected by CKDu. Monthly averages of the daily maximum temperatures between 1996 and 2014 were also compared to concurrent weather data from eight Automated Surface Observing System Network weather stations across Nicaragua. Our objectives were to assess changes in temperature across harvest seasons, estimate the number of days that workers were at risk of heat-related illness and compare daily maximum temperatures across various sites in Nicaragua. The monthly average daily maximum temperature during the harvest season increased by 0.7 °C per decade between 1973 and 1990. The number of days per harvest season with a maximum temperature over 35 °C increased by approximately five days per year between 1974 and 1990, from 32 days to 114 days. Between 1991 and 2013, the number of harvest days with a maximum temperature over 35 °C decreased by two days per year, and the monthly average daily maximum temperature decreased by 0.3 °C per decade. Comparisons with weather stations across Nicaragua demonstrate that this company is located in one of the consistently hottest regions of the country.

Keywords: Central America; heat stress; historical weather trends; occupational heat exposure.

Figure 1

One-year (black line) and five-year (red line) rolling averages of monthly-averaged daily maximum temperatures at ISA, all months in the period May 1973–November 2013.

Figure 2

Number of days during harvest months (December–May) with a maximum temperature over 35 °C, 1974–2013, with 5-year rolling average (red line).

Figure 3

Distributions of all daily HI summaries calculated using three combinations of mean and maximum temperature and humidity, 2000–2014.

Figure 4

Histograms of monthly-averaged daily maximum temperatures at all seven ASOS Network monitors and ISA, 1996–2014, and map of the locations of each monitor.