Baseline facial emotion recognition is associated with clinical decline across the Alzheimer’s disease spectrum: a multi-instrument longitudinal assessment study

Background Facial emotion recognition (FER) is increasingly recognized as a functionally relevant domain in the Alzheimer’s disease (AD) spectrum, yet whether baseline FER is associated with subsequent clinical decline remains insufficiently established. Methods We studied 328 participants [subjective cognitive decline (SCD) n = 94, mild cognitive impairment (MCI) n = 142, AD dementia n = 92] from a longitudinal memory clinic cohort; 148 had follow-up assessments (mean 1.59 ± 0.67 years). FER was assessed using the Korean version of the Florida Affect Battery (K-FAB; five subtests, FER_mean). Linear mixed-effects models examined group-differential trajectories of the Mini-Mental State Examination (MMSE), Clinical Dementia Rating–Sum of Boxes (CDR-SOB), and FER_mean, adjusted for age, sex, education, and baseline values. Results FER_mean decreased stepwise across groups at baseline (SCD 17.3 ± 1.5, MCI 16.4 ± 2.1, AD 15.3 ± 2.0; p < 0.001). CDR-SOB showed more consistent group-differential longitudinal trajectories: MCI increased at +0.550 points/year ( p < 0.001), with SCD significantly slower ( β = −0.491, p = 0.008) and AD faster ( β = +0.371, p = 0.038). FER_mean showed a modest decline in MCI ( β = −0.169/yr., p = 0.078) and SCD showed significantly attenuated decline relative to MCI ( β = +0.376, p = 0.035). Lower baseline FER was associated with faster CDR-SOB worsening ( ρ = −0.221, p = 0.006) but not MMSE decline ( ρ = 0.093, p = 0.255). FER change rates showed a weak, non-significant correlation with MMSE change ( ρ = 0.004, p = 0.960) but a modest significant correlation with CDR-SOB change ( ρ = −0.195, p = 0.018), suggesting partially distinct longitudinal patterns. Conclusion Baseline FER was modestly associated with longitudinal worsening in clinical severity (CDR-SOB), but not cognitive screening performance (MMSE) across the pre-dementia to dementia spectrum. FER trajectories showed limited correlation with traditional measures. These findings indicate that FER may have a potential complementary role of social cognitive assessment in the AD continuum, pending further validation.