Drought and All-Cause Mortality in All Age Groups in Nebraska

Drought, as labeled by United Nations, is the most far-­reaching of all natural hazards and has likely caused more deaths internationally than any other climate-related event. The health outcomes from drought, unlike other well-studied hazards such as hurricanes, are typically better understood for regions outside the United States. Drought’s slow-evolving nature and delayed impacts make health studies more challenging, as the health outcomes are mainly indirect. Droughts are a common occurrence in the United States, degrading land and water resources. As the intensity and frequency of the droughts are projected to increase by the end of the century, it is of vital significance to investigate the causal pathways, in which drought affect human health outcomes. The primary objective of this study is to better understand the linkages between drought and all-cause mortality in Nebraska. Our primary exposure variable was an annual cumulative drought intensity score based on the 12-month county-level Evaporative Demand Drought Index from 1980 to 2014. The outcome variable of demographic subgroup-specific all-cause mortality count data per-year were obtained from the National Vital Statistics System from the United States Centers for Disease Control and Prevention’s (CDC). We used Bayesian Zero-Inflated Negative Binomial regression with random effects to model the mortality in each county-stratum-year for each combined age-race-gender stratum against the drought index. Our primary results show that for most demographic subgroups, there is no significant association between drought intensity and overall mortality. Among the significant results, the white race group, males and females aging 45 to 64, had the greatest number of significant Incidence rate ratios suggesting increasing mortality rates with increasing drought severity. The results of this study will help to identify regions and populations in Nebraska that are most vulnerable to drought, so appropriate messaging can be developed to mitigate such negative health impacts.