Cognitive impairment in older adults with type 1 diabetes: Influence of premorbid ability and associations with depression, anxiety, and diabetes-related distress

Objective: This study characterised cognitive and psychological functioning in older adults with type 1 diabetes (T1D), compared the prevalence of cognitive impairment under age-based and premorbid-ability+age-adjusted (PA+AA) norms, and examined associations between cognitive status and depression, anxiety, and diabetes-related distress. Method: Forty-three adults aged ≥55 years with T1D completed a comprehensive neuropsychological assessment covering attention, working memory, verbal and visuospatial memory, processing speed, executive function, verbal fluency, and confrontation naming, alongside measures of depression (PHQ-9), anxiety (GAD-7), and diabetes-related distress (PAID-11). Impairment was defined as performance ≥1.5 SD below expected levels on at least two tests, with expected scores derived from either age-based norms or estimated premorbid ability combined with age. Results: Group-level performance was within or above age-expected ranges. Individually, 14% met criteria for impairment under age-based norms versus 42% under PA+AA norms; the additional 28% were identified only against estimated prior ability. Impairments were most frequent in confrontation naming and processing speed. PA+AA norms additionally revealed impairments in attention, working memory, verbal fluency, and cognitive flexibility. Impaired participants reported significantly higher depression under both approaches. Anxiety was significantly elevated under PA+AA norms, and diabetes-related distress under age-based norms only. Conclusions: Age-based norms may substantially underestimate cognitive impairment in older adults with T1D, particularly among those with higher premorbid ability. The association between impairment and elevated psychological distress supports the integration of cognitive and mood assessment in routine diabetes care.