Longitudinal assessment of dementia measures in Down syndrome

Introduction: Early detection of dementia symptoms is critical in Down syndrome (DS) but complicated by clinical assessment barriers. The current study aimed to characterize cognitive and behavioral impairment using longitudinal trajectories comparing several measures of cognitive and behavioral functioning. Methods: Measures included global cognitive status (Severe Impairment Battery [SIB]), motor praxis (Brief Praxis Test [BPT]), and clinical dementia informant ratings (Dementia Questionnaire for People with Learning Disabilities [DLD]). One-year reliability was assessed using a two-way mixed effect, consistency, single measurement intraclass correlation among non-demented participants. Longitudinal assessment of SIB, BPT, and DLD was completed using linear mixed effect models. Results: One-year reliability (n = 52; 21 male) was moderate for DLD (0.69 to 0.75) and good for SIB (0.87) and BPT (0.80). Longitudinal analysis (n = 72) revealed significant age by diagnosis interactions for SIB (F(2, 115.02) = 6.06, P =.003), BPT (F(2, 85.59) = 4.56, P =.013), and DLD (F(2, 103.56) = 4.48, P =.014). SIB progression (PR) had a faster decline in performance versus no-dementia (ND) (t(159) = −2.87; P =.013). Dementia had a faster decline in BPT performance versus ND (t(112) = −2.46; P =.041). PR showed quickly progressing scores compared to ND (t(128) = −2.86; P =.014). Discussion: Current measures demonstrated moderate to good reliability. Longitudinal analysis revealed that SIB, BPT, and DLD changed with age depending on diagnostic progression; no change rates were dependent on baseline cognition, indicating usefulness across a variety of severity levels in DS.