Survival Analysis in Primary Progressive Apraxia of Speech and Agrammatic Aphasia

Objective To compare survival among patients with different combinations of apraxia of speech (AOS) and agrammatic aphasia, including those with isolated AOS (primary progressive AOS, PPAOS), both AOS and agrammatic aphasia (AOS + progressive agrammatic aphasia [PAA]), and isolated agrammatic aphasia (PAA). Methods One hundred nine patients were recruited who had any combination of AOS and agrammatic aphasia (42 PPAOS, 56 AOS + PAA, and 11 PAA) and were followed longitudinally, with 57 patients having since died. Cox proportional hazard models were used to quantify the relative risk of death across diagnoses. Adjusted survival curves are presented based on this model. We also assessed the influence of AOS and aphasia severity on survival. Results PPAOS had the longest survival (median survival of 5.97 years from the baseline visit), followed by PAA (5.26 years) and then AOS + PAA (4.33 years). AOS + PAA had a greater risk of death than PPAOS, with a hazard ratio of 3.01 (lower/upper confidence interval = 1.66/5.46, p < 0.001). Risk of death did not differ between PAA and the other groups. All results accounted for age and time from onset to baseline visit. AOS severity, independent of syndromic diagnosis, was associated with greater risk of death, with a hazard ratio of 1.35 for a 1-point increase in severity. Aphasia severity was not associated with risk of death. Conclusions Individuals with PPAOS have better survival and reduced risk of death compared with individuals with AOS + PAA. This finding will help improve prognostic estimates for these patients and supports the value of distinguishing PPAOS from AOS + PAA.