Analysis of 45,876 alcohol-associated emergency department visits (weighted national estimate: ~2.09 million) drawn from NEISS surveillance data spanning 2019–2025 finds that injury risk peaks with calendar-stable precision in early-to-mid July for adults aged 25–64, with jackknife leave-one-year-out resampling shifting peak estimates by no more than 14 days. Adults 65 and older, however, showed profound temporal instability — up to 100 days of peak-day drift across iterations — driven almost entirely by women 65+, whose jackknife range spanned 332 days, clustering in late October through early January. Males 65+ remained relatively stable, peaking in early August. Hospital admission rates climbed monotonically with age, reaching 31.8% in the oldest group versus 9.0% in adults 18–24.
The finding matters because it challenges a one-size-fits-all summer intervention model. Public health campaigns and ED screening intensification timed to summer months may systematically miss older women, who face the highest hospitalization burden. The late-autumn to early-winter clustering in that group invites hypotheses around holiday drinking, social isolation, and medication interactions common in older females — none of which this observational dataset can resolve causally.
Critical limitations apply: NEISS sampling is designed for injury surveillance, not alcohol epidemiology, and the Alcohol_Involved field was only standardized in 2019, limiting the time series. As a preprint not yet peer-reviewed, these results remain provisional and should be interpreted cautiously before informing clinical protocols.