Drought and cognitive function in older adults: results from the Mexican health and aging study.

Longer drought exposure was negatively associated with Verbal Learning and Verbal Recall performance in older Mexican adults.

• Sample consisted of adults aged 50+ from the Mexican Health and Aging Study (n = 6988).
• Drought exposure was quantified both as total number of months of drought exposure and as longest streak of consecutive months of drought exposure.
• The major drought evaluated occurred between 2010 and 2012 in Mexico.
• Findings were consistent whether using total months or longest consecutive streak of drought exposure.

Drought exposure showed an inverse U-shaped association with Verbal Fluency performance.

• Unlike Verbal Learning and Verbal Recall, Verbal Fluency did not show a simple linear negative relationship with drought exposure.
• This inverse U-shaped pattern was observed whether drought was quantified as total months or longest consecutive streak.
• The pattern held across various thresholds of drought severity, including severe to exceptional drought.

Associations between drought exposure and cognitive function were not explained by nutritional or mental health covariates.

• Multilevel regression models controlled for pre-drought cognition and nutritional/mental health covariates.
• Despite drought being previously linked to poorer mental health and nutritional outcomes, these pathways did not account for the observed cognitive associations.
• Inverse probability of attrition weighting was employed to address potential selection bias from participant dropout.

The study linked municipality-level drought monitor data to individual-level survey data across pre-drought and post-drought periods.

• Individual-level data were drawn from the Mexican Health and Aging Study waves in 2003 (pre-drought) and 2012 (post-drought).
• Monthly municipality-level drought exposure data came from the Mexican Drought Monitor produced by the Mexican National Water Commission.
• Multilevel regression models were used to examine how length of drought exposure related to post-drought cognition while controlling for pre-drought cognition.

Findings on drought and cognition were robust across various thresholds of drought severity.

• Analyses were conducted using various thresholds of drought severity, specifically severe to exceptional drought.
• Results for both Verbal Learning/Recall and Verbal Fluency were similar across these different severity thresholds.
• Both total months of drought and longest streak of consecutive months yielded similar findings.