Many people notice that hangovers become more severe with age, even when drinking the same amount or less than they used to. This isn't imagination — it's biology. Several physiological changes explain why hangover tolerance decreases over time. First, liver enzyme efficiency declines with age. The enzyme alcohol dehydrogenase (ADH), which breaks down ethanol into acetaldehyde, becomes less efficient after age 30–35. This means alcohol stays in your system longer, and the toxic intermediate metabolite acetaldehyde — responsible for nausea, headache, and flushing — accumulates more before being cleared (NIAAA, 2023). Second, body composition changes. As you age, total body water decreases and body fat percentage increases, even if your weight stays stable. Since alcohol distributes through body water, less water means higher BAC from the same number of drinks. A 30-year-old and a 50-year-old drinking identical amounts will reach different peak BAC levels. Third, sleep quality declines naturally with age, and alcohol's sleep-disrupting effects compound this. Older adults get less deep sleep and REM sleep to begin with, so alcohol's suppression of these stages has a proportionally larger impact on recovery. Fourth, chronic low-grade inflammation increases with age (a process called inflammaging), and alcohol triggers additional inflammatory responses through cytokine release. Research shows that hangover severity correlates more strongly with inflammatory biomarkers than with BAC itself (Penning et al., 2012). Finally, functional tolerance — the brain's adaptation to alcohol's subjective effects — can mask how much you're actually consuming. You feel "fine" while drinking but haven't built equivalent tolerance to the metabolic aftermath. Sources: NIAAA, Penning et al. (2012) "The Alcohol Hangover Research Group" — PubMed, Verster et al. (2019).