Objectives Mesoamerican nephropathy is an epidemic of chronic kidney disease (CKD) unrelated to traditional causes, mostly observed in sugarcane workers. We analysed CKD mortality in Costa Rica to explore when and where the epidemic emerged, sex and age patterns, and relationship with altitude, climate and sugarcane production.

Methods SMRs for CKD deaths (1970–2012) among population aged ≥20 were computed for 7 provinces and 81 counties over 4 time periods. Time trends were assessed with age-standardised mortality rates. We qualitatively examined relations between mortality and data on altitude, climate and sugarcane production.

Results During 1970–2012, age-adjusted mortality rates in the Guanacaste province increased among men from 4.4 to 38.5 per 100 000 vs 3.6–8.4 in the rest of Costa Rica, and among women from 2.3 to 10.7 per 100 000 vs 2.6–5.0 in the rest of Costa Rica. A significant moderate excess mortality was observed among men in Guanacaste already in the mid-1970s, steeply increasing thereafter; a similar female excess mortality appeared a decade later, remaining stable. Male age-specific rates were high in Guanacaste for age categories ≥30, and since the late 1990s also for age range 20–29. The male spatiotemporal patterns roughly followed sugarcane expansion in hot, dry lowlands with manual harvesting.

Conclusions Excess CKD mortality occurs primarily in Guanacaste lowlands and was already present 4 decades ago. The increasing rates among Guanacaste men in hot, dry lowland counties with sugarcane are consistent with an occupational component. Stable moderate increases among women, and among men in counties without sugarcane, suggest coexisting environmental risk factors.