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Primary Submission Category: Environmental factors
Cold and hot temperatures are associated with increased mortality risk among incarcerated adults in California state prisons
Authors: Lisa Frueh, Jessica Simes, Henry Willis, Allan Just, Jaquelyn Jahn,
Presenting Author: Lisa Frueh*
Background: Growing epidemiologic evidence has documented effects of ambient temperature on the health of incarcerated populations, who are particularly vulnerable due to aging prison infrastructure and poor climate control. Our goal was to identify associations between ambient temperature and mortality among people incarcerated in California.
Methods: We examined all deaths in California state prisons from 2005–24, excluding those occurring out of state, in community-based facilities, or hospitals. Daily ambient temperature at each facility was estimated using hybrid spatiotemporal models. Using a facility-level time series design with distributed lag nonlinear models (lags 0–6) with a population offset, adjusted for day of week and nonlinear time trends, we assessed associations between minimum daily temperature and deaths.
Results: Among 7,617 deaths across 34 facilities, both cold and hot minimum daily temperature were associated with increased mortality risk (though confidence intervals crossed the null). Compared to the minimum mortality temperature (MMT) of 19.7°C, the cumulative relative risk (RR) at 11°C (10th ptile) was 1.026 (0.956, 1.101) and RR at 39°C (90th ptile) was 1.123 (0.75, 1.682). When comparing temperature effects across facilities with different cooling regimes, the bulk of deaths (72%) occurred in facilities with evaporative or no cooling, but heat-related risks were concentrated in facilities with refrigeration cooling (RR for 90th percentile vs. MMT = 1.088 [0.612, 1.935]). Across cooling types, cold temperatures were associated with increased mortality risk. For extreme cold in facilities with refrigeration (<1st percentile), the cumulative RR was statistically significant: 1.698 (1.031, 2.799).
Significance: We identified elevated risk of mortality associated with hot but especially cold temperatures among incarcerated people in California state prisons, though confidence intervals crossed the null. These findings highlight thermal control as a modifiable factor to improve the health of incarcerated populations.