Speech and phonological impairment across Alzheimer's disease severity

Introduction: Phonetic-phonological impairments have been described in dementia due to Alzheimer's disease (AD). However, whether the likely phonological-linguistic changes progress with the evolution of the disease or whether phonetic-motor manifestations occur in all three stages of AD (mild, moderate, and severe) has not yet been clarified. Thus, the aim of this study was to verify whether phonological-linguistic and phonetic-motor speech manifestations occur in the mild, moderate, and severe stages of AD. Methods: Thirty participants in each stage of probable AD (mild, moderate, and severe) and 30 healthy older adults underwent cognitive, instrumental activities of daily living and phonetic-phonological assessments. Phonetic-phonological manifestations were classified into three types: likely phonetic-motor, likely phonological-linguistic, and manifestations that may occur in disorders of both phonetic and phonological origin. Results: The manifestations analyzed in this study occurred rarely. The manifestations that may occur in disorders of both phonetic and phonological origin were the most common in all stages of the disease. The likely phonetic-motor manifestations emerged during the mild stage of the disease (distortions, prolonged intersegment duration, and vowel prolongations), while the likely phonological-linguistic manifestations were present mainly in the moderate (substitutions and attempts at the word level) and severe stages (substitutions, attempts at the word level, self-corrections, and anticipations). The occurrence of phonetic-phonological manifestations increased with disease progression. Conclusions: The type of phonological and phonetic manifestations in the individuals with AD differed according to the dementia stage and were statistically more frequent as dementia worsened.