Speech and language therapy interventions for subgroups of people with aphasia

Overview

We undertook prespecified subgroup analyses to explore language change in the context of SLT frequency, duration, intensity and dosage, and whether or not the findings varied by participants’ age, time since aphasia onset and aphasia severity. Building on the preceding results (see Chapters 4–6), the post hoc subgroup analysis also considered whether or not language gains made by males and females varied in the context of different SLT interventions. Reflecting IPD availability, we restricted these subgroup analyses to four language domains (overall language ability, auditory comprehension, naming and functional communication) and to IPD from RCT data sets only. We considered data set variability for each analysis.

Speech and language therapy and language outcomes by subgroup

Subgroup analyses were conducted using IPD network meta-analysis (see Chapter 6) to evaluate participants’ language gains according to baseline criteria: age, time since aphasia onset and stroke severity. In the context of the observations in relation to language recovery and sex (Chapters 4–6) and the known relationship between sex and other stroke outcomes, we included a post hoc comparison between female and male participants’ responses to SLT on language outcomes.

We had functional communication (observer-rated) data from some participants on the TOMs activity and participation subtests. Previously, we found no indication that the choice of which TOMs subtest to include in the analysis affected the findings (see Chapter 6 and Appendix 9, Tables 16–18). Thus, we conducted the subgroup analysis inclusive of the TOMs activity data only.

We dichotomised RCT participants based on their median baseline language score, age (± 65 years), time since aphasia onset at baseline (± 3 months) and sex. To represent the entire database population, median baseline language scores were calculated from all RCT and non-RCT IPD, regardless of the availability of SLT regimen or follow-up data. Age, however, was dichotomised, to reflect the age groups used earlier in the analysis (≤ 65 years and > 65 years; see Chapters 5 and 6) rather than the median of all IPD (which was 63 years; see Chapter 3).

We considered relative variance, highlighting analyses where it exceeded 25%. We report variance that exceeded 50% in the tables for completeness, but we do not include such results when reporting the findings. Across the subgroups (and when significant changes from baseline were observed), generally we continued to see the highest gains in language performance from baseline among the participants aged < 65 years, females and those who received SLT within 3 months of the index stroke (Table 10).

Age

We investigated whether or not the younger (≤ 65 years; 277 IPD) and older participants’ (> 65 years; 205 IPD) language recoveries differed in the context of SLT variations. Relative variance was modest (< 50%) across comparisons.

Age and speech and language therapy frequency

Younger participants gained most on overall language ability (measured on the WAB-AQ) in the context of SLT 5 or more days weekly [15.12 points, 95% CI 8.15 to 22.08 points (107 IPD; 6 RCT)], and older participants gain most when they received SLT more than 5 days weekly [17.19 points, 95% CI 3.85 to 30.53 points (10 IPD; 2 RCT)]. Younger and older participants’ auditory comprehension (measured on the TT-AAT) made the best gains when SLT occurred 4 or more days weekly [young: 6.78 points, 95% CI 2.33 to 11.22 points (64 IPD; 5 RCTs); old: 8.48 points, 95% CI 2.04 to 14.93 points (50 IPD; 3 RTCs)]. Similarly, both groups made the highest naming gains (measured on the BNT) in the context of receiving SLT up to 2 days weekly [young: 15.02 points, 95% CI 8.95 to 21.10 points (26 IPD; 4 RCTs); old: 9.83 points, 95% CI 2.44 to 17.22 points (16 IPD; RCTs 4)]. Younger participants gained most functional communication (measured on the AAT-SSC) alongside SLT occurring more than 5 days weekly [1.18 points, 95% CI 0.28 to 2.08 points (but based only on 3 IPD; 2 RCTs)], whereas the older group gained most when SLT occurred at least 4 or 5 days weekly [0.78 points, 95% CI 0.15 to 1.40 points (54 IPD; 3 RCTs)] (see Appendix 30, Table 34, and Appendix 34, Table 38).

Age and speech and language therapy duration

The younger group’s greatest overall language [22.69 points (95% CI 15.20 to 30.19 points) on the WAB-AQ (25 IPD; 3 RCTs)], auditory comprehension [8.41 points (95% CI 2.62 to 14.20 points) on the TT-AAT (60 IPD; 5 RCTs)] and naming gains [11.27 points (95% CI 5.44 to 17.11 points) on the BNT (59 IPD; 4 RCTs)] were associated with between 10 and 20 weeks of SLT. In contrast, the older participants’ greatest gains in overall language [20.60 points (95% CI 7.77 to 33.42 points) on the WAB-AQ (15 IPD; 2 RCTs)] and naming [11.23 points (95% CI 2.03 to 20.43 points) on the BNT (71 IPD; 3 RCTs)] occurred when SLT lasted for > 20 weeks. We found no evidence of significant auditory comprehension gains for the older group (see Appendix 30, Table 34, and Appendix 34, Table 38).

Age and speech and language therapy intensity

Younger participants made the best overall language ability [16.97, 95% CI 9.96 to 23.98 (78 IPD; 3 RCTs)] and auditory comprehension gains [8.96 points, 95% CI 5.35 to 12.56 points (108 IPD; 4 RCTs)] alongside > 9 hours of SLT weekly. Although the older group’s best auditory comprehension gains were also associated with > 9 hours of SLT weekly [5.34 points (95% CI 0.67 to 10.02 points) on the TT-AAT (33 IPD; 6 RCTs)], their best overall language gains occurred when SLT was received for up to 2 hours weekly [16.92 points (95% CI 3.80 to 30.04 points) on the WAB-AQ (37 IPD; 3 RCTs)]. Similarly, SLT for up to 2 hours weekly was also associated with the highest naming gains (measured on the BNT) for both groups [young: 17.35 points, 95% CI 8.32 to 26.38 points (10 IPD; 2 RCTs); old: 11.12 points, 95% CI 1.41 to 20.82 points (8 IPD; 2 RCTs)], although this finding was based on small IPD and data set numbers. Whereas the older group also made their highest functional communication gains [0.97 points (95% CI 0.38 to 1.57 points) on the AAT-SSC (41 IPD; 4 RCT)] in the context of receiving SLT for up to 2 hours weekly, younger participants’ greatest functional communication gains were associated with 3–4 hours of SLT weekly [0.87 points (95% CI 0.53 to 1.22 points) on the AAT-SSC (74 IPD; 5 RCTs)] (see Appendix 30, Table 34, and Appendix 34, Table 38).

Age and speech and language therapy dosage

In the context of a total SLT dosage of 20–50 hours, both younger and older age groups made their highest gains on overall language ability (as measured on the WAB-AQ) [young: 23.38 points, 95% CI 13.47 to 33.28 points (15 IPD; 3 RCTs); old: 15.95 points, 95% CI 5.08 to 26.83 points (16 IPD; 4 RCTs)], auditory comprehension (as measured on the TT-AAT) [young: 6.06 points, 95% CI 1.75 to 10.36 points (59 IPD; 6 RTCs); old: 5.80 points, 95% CI 1.35 to 10.24 points (34 IPD; 7 RCTs)] and naming (as measured on the BNT) [young: 13.56 points, 95% CI 5.30 to 21.79 points (57 IPD; 5 RCTs); old: 8.32 points, 95% CI 0.55 to 16.08 points (24 IPD; 5 RCTs)] (see Appendix 30, Table 34, and Appendix 34, Table 38). Similarly, the older group’s highest functional communication gains (as measured on the AAT-SSC) were also associated with the same dosage of 20–50 SLT hours [0.86 points, 95% CI 0.36 to 1.36 points (31 IPD; 9 RCTs)], whereas the younger group’s gains were best when SLT lasted 14–20 hours [1.12 points, 95% CI 0.47 to 1.78 points (6 IPD; 3 RCTs)] (see Appendix 32, Table 34, and Appendix 34, Table 38).

Time since aphasia onset

Participants for whom it was ≤ 3 months since their aphasia onset (early group: 324 IPD) showed higher change scores across all domains than participants for whom it was > 3 months after stroke (late group: 158 IPD), potentially reflecting spontaneous recovery alongside SLT intervention benefits. Relative variance was modest (< 50%) across comparisons (see Appendix 30, Table 34, and Appendix 34, Table 39).

Time since onset and speech and language therapy frequency

The highest gains for the early group on overall language [27.75 points (95% CI 3.56 to 51.93 points) on the WAB-AQ (3 IPD; 1 RCT)] were seen alongside SLT 3 days per week, but this was based on few participants and one dataset. The next highest gain for the early group [21.42 points (95% CI 13.45 to 29.39 points); 150 IPD; 5 RCTs] occurred alongside SLT that was delivered 5 days weekly, which was when the late group’s highest gains were also observed [6.32 points (95% CI 1.58 to 11.07 points); 44 IPD; 1 RCT]. The early group’s best functional communication gains [1.55 points (95% CI 0.59 to 2.52 points) on the AAT-SSC (80 IPD; 1 RCT)] were seen when SLT was delivered three or four times weekly. The late group made no significant gains on functional communication (see Appendix 30, Table 34, and Appendix 34, Table 39).

The highest naming gains (measured on the BNT) for the early group [16.96 points, 95% CI 7.68 to 26.24 points (33 IPD; 3 RCTs)] were associated with SLT twice weekly, whereas the late group made their only significant gain alongside SLT 3 days weekly [2.81 points, 95% CI 0.60 to 5.02 points (78 IPD; 3 RCTs)]. The late group’s best auditory comprehension gains were associated with SLT 4 or 5 days weekly [3.71 points (95% CI 1.41 to 6.00 points) on the TT-AAT (89 IPD; 5 RCTs)], and we found no evidence of significant auditory comprehension gains for the early group in this analysis (see Appendix 30, Table 34, and Appendix 34, Table 39).

Time since onset and speech and language therapy duration

There was no clear pattern in relation to SLT duration and best language gains by time since stroke. The early group made the best overall language ability gains [24.73 points (95% CI 12.53 to 36.92 points) on the WAB-AQ (26 IPD; 3 RCTs)] when SLT lasted > 4–10 weeks, best functional communication gains [1.16 points (95% CI 0.56 to 1.77 points) on the AAT-SSC (40 IPD; 3 RCTs)] when SLT lasted at least 10–20 weeks and best naming gains [12.50 points (95% CI 0.39 to 24.61 points) on the BNT (86 IPD; 3 RCTs)] in the context of > 20 weeks of SLT. Relative variance for auditory comprehension analysis and the early group was unacceptably high, at > 50% (see Appendix 30, Table 34, and Appendix 34, Table 39).

The late group’s best overall language ability [9.30 points (95% CI 3.12 to 15.48 points) on the WAB-AQ (14 IPD; 1 RCT)] and auditory comprehension gains [5.20 points (95% CI 2.52 to 7.88 points) on the TT-AAT (49 IPD; 1 RCT)] were both associated with > 20 weeks of SLT. The late group’s best (and only significant) naming gains occurred with > 10–20 weeks of SLT [4.12 points (95% CI 1.79 to 6.45 points) on the BNT (33 IPD; 2 RCTs)]. Significant gains for the late group’s functional communication were not evident in this analysis.

Time since onset and speech and language therapy intensity

The early group’s highest overall language ability [24.27 points (95% CI 13.37 to 35.18 points) on the WAB-AQ (62 IPD; 2 RCTs)], naming [the only significant gain noted was 17.66 points (95% CI 3.95 to 31.36 points) on the BNT (10 IPD; 1 RCT)] and functional communication gains [1.29 points (95% CI 0.64 to 1.95 points) on the AAT-SSC (57 IPD; 2 RCTs)] were associated with receiving SLT for up to 2 or 3 hours weekly. The late group made their best overall language [6.25 points (95% CI 2.19 to 10.32 points) on the WAB-AQ (25 IPD; 2 RCTs)] and naming gains [5.58 points (95% CI 3.56 to 7.60 points) on the BNT (27 IPD; 2 RCTs)] alongside 3–4 hours of SLT weekly. In contrast, both early and late groups’ only auditory comprehension gains (measured on the TT-AAT) occurred in the context of > 9 hours of SLT weekly [early: 9.26 points, 95% CI 2.04 to 16.47 points (20 IPD; 2 RCT); late: 4.60 points, 95% CI 2.43 to 6.77 points (121 IPD; 4 RCTs)] (see Appendix 30, Table 34, and Appendix 34, Table 39).

Time since onset and speech and language therapy dosage

Early-group participants achieved their greatest overall language [27.52 points (95% CI 18.32 to 36.71 points) on the WAB-AQ (27 IPD; 3 RCTs)], naming [20.67 points (95% CI 2.87 to 38.47 points) on the BNT (31 IPD; 2 RCTs)] and functional communication gains [1.25 points (95% CI 0.69 to 1.81 points) on the AAT-SSC (31 IPD; 3 RCTs)] in the context of between 20 and 50 hours of SLT. The late group also achieved their best (and only) significant naming gain alongside 20–50 hours of SLT [3.02 points (95% CI 0.90 to 5.15 points) on the BNT (50 IPD; 4 RCTs)], but, in contrast to the early group, their highest overall language [10.11 points (95% CI 4.22 to 16.0 points) on the WAB-AQ (15 IPD; 1 RCT)] and auditory comprehension gains [4.17 points (95% CI 1.68 to 6.66 points) on the TT-AAT (76 IPD; 3 RCT)] were associated with ≥ 50 and ≥ 14 hours of SLT in total. No significant gains from baseline were observed on measures of functional communication for the late group (see Appendix 30, Table 34, and Appendix 34, Table 39).

Aphasia severity

Based on their language abilities at baseline, participants were dichotomised into mild–moderate (253 IPD) and moderate–severe aphasia groups (280 IPD). For each domain, median transformed language scores on the anchor measures, together with all available IPD in the RELEASE study database, supported the creation of two aphasia severity groups (see Appendix 34, Table 40). Across all domains, participants with moderate–severe aphasia achieved higher gains from baseline than those with mild–moderate aphasia. It is possible that the mild–moderate group’s recovery on the anchor measures may have been masked by the assessments’ ceiling effects, whereas the moderate–severe group had more scope to improve (see Appendix 30, Table 34, and Appendix 34, Table 40).

Severity and speech and language therapy frequency

The moderate–severe group’s highest overall language [18.25 points (95% CI 8.04 to 28.46 points) on the WAB-AQ (38 IPD; 5 RCTs)] and auditory comprehension gains [8.48 points (95% CI 3.67 to 13.28 points) on the TT-AAT (80 IPD; 5 RCTs)] were associated with receiving SLT 3 to 4 days weekly. The moderate–severe group’s best naming gains were associated with receiving SLT up to twice weekly [13.07 points (95% CI 6.99 to 19.14 points) on the BNT (36 IPD; 4 RCTs)], and their best functional communication gains were associated with receiving SLT 4 days weekly [1.00 points (95% CI 0.48 to 1.51 points) on the AAT-SSC (55 IPD; 2 RCTs)].

The analysis found for the mild–moderate group, but their best gains for overall language and functional communication occurred when SLT occurred over at least 5 days weekly [9.85 points (95% CI 4.37 to 15.33 points) on the WAB-AQ (16 IPD; 2 RCTs)] and [0.66 points (95% CI 0.36 to 0.96) on the AAT-SSC (55 IPD; 8 RCTs)], respectively. Their best gains for naming [11.11 points (95% CI 5.61 to 16.60 points) on the BNT (11 IPD; 3 RCTs)] occurred when SLT took place 5 days weekly. These findings were based on small IPD numbers and data sets and should be interpreted with caution. Relative variance was unacceptably high (> 50%) for the analysis relating to the mild–moderate group’s auditory comprehension (see Appendix 30, Table 34, and Appendix 34, Table 40).

Severity and speech and language therapy duration

The moderate–severe group’s best language gains on measures of overall language ability [23.53 points (95% CI 12.09 to 34.96 points) on the WAB-AQ (18 IPD; 2 RCTs)], functional communication [1.14 points (95% CI 0.78 to 1.49 points) on the AAT SSC (61 IPD; 4 RCTs)] and auditory comprehension [10.61 points (95% CI 3.91 to 17.30 points) on the TT-AAT (105 IPD; 3 RCTs)] were associated with SLT lasting > 20 weeks. Few significant changes were observed among the mild–moderate group, but their best overall language [10.01 points (95% CI 2.42 to 17.60 points) on the WAB-AQ (16 IPD; 2 RCTs)] and naming gains [16.01 points (95% CI 6.60 to 25.41 points) on the BNT (26 IPD; 2 RCTs)] were also seen alongside SLT that lasted in excess of 20 weeks. For the moderate–severe group, the highest naming gains were associated with > 10–20 weeks of SLT [7.52 points (95% CI 1.08 to 13.97 points) on the BNT (71 IPD; 4 RCTs)]. Relative variance for auditory comprehension analysis and the mild-moderate group was unacceptably high, at > 50% (see Appendix 30, Table 34, and Appendix 34, Table 40).

Severity and speech and language therapy intensity

The moderate–severe group achieved their highest auditory comprehension [9.07 points (95% CI 2.57 to 15.58 points) on the TT-AAT (9 IPD; 2 RCTs)] and naming gains [12.45 points (95% CI 4.25 to 20.64 points) on the BNT (16 IPD; 2 RCTs)] in the context of up to 2 hours of SLT weekly, but IPD and RCT numbers were very low. The greatest overall language ability [20.04 points (95% CI 10.14 to 29.94 points) on the WAB-AQ (64 IPD; 4 RCTs)] and functional communication gains [0.98 points (95% CI 0.40 to 1.55 points) on the AAT-SSC (20 IPD; 4 RCTs)] for the moderate–severe group were associated with ≤ 2 and up to 3 SLT hours weekly and (on some measures) in excess of 9 hours weekly. For the mild–moderate group, the best gains on overall language ability [7.97 points (95% CI 3.37 to 12.57 points) on the WAB-AQ (48 IPD; 3 RCTs)] and naming [9.45 points (95% CI 4.64 to 14.26 points) on the BNT (19 IPD; 4 RCTs)] occurred in the context of > 9 hours of SLT weekly with similar gains at other SLT intensities. Similarly, functional communication gains for the mild-moderate group were highest when SLT was > 4 and up to 9 hours weekly [0.63 points (95% CI 0.26 to 1.01) on the AAT-SCC (27 IPD, 4 RCTs)]. Relative variance was unacceptably high (> 50%) for the mild–moderate group’s auditory comprehension analysis (see Appendix 30, Table 34, and Appendix 34, Table 40).

Severity and dosage

Both severity groups made their greatest gains on overall language ability (as measured on the WAB-AQ) with at least 20–50 hours of SLT [moderate–severe group: 23.49 points, 95% CI 13.50 to 33.48 points (23 IPD; 3 RCTs); mild–moderate group: 8.73 points, 95% CI 1.95 to 15.51 points (8 IPD; 2 RCTs)]. The moderate–severe group’s highest auditory comprehension and functional communication gains were associated with > 50 hours of SLT [8.89 points (95% CI 4.49 to 13.30 points) on the TT-AAT (142 IPD; 6 RCTs)], and [1.07 points (95% CI 0.78 to 1.37 points)] on the AAT-SSC (72 IPD; 6 RCTs)]. The mild–moderate group’s highest naming gains were associated with a SLT dosage in excess of 100 hours [12.96 points (95% CI 8.51 to 17.41 points) on the BNT (11 IPD; 3 RCTs)]. Relative variance was unacceptably high (> 50%) for naming gains (moderate–severe group) and auditory comprehension (mild–moderate group) analysis (see Appendix 30, Table 34, and Appendix 34, Table 40).

Sex

Generally, female participants (211 IPD) had higher language gains across all domains than male participants (329 IPD), although these differences declined with increasing age (> 66 years for naming and > 75 years for functional communication). Interestingly, the best overall language gains for the oldest females [> 75 years: 16.6 points (95% CI 8.38 to 24.89 points) on the WAB-AQ (68 IPD; 6 RCTs)] were similar to those of the youngest females [≤ 55 years: 16.3 points, 95% CI 8.84 to 23.72 points (55 IPD; 10 RCTs)] (see Appendix 30, Table 34, and Appendix 34, Table 38). Relative variance was modest (< 50%) (see Appendix 30, Table 34, and Appendix 34, Table 41).

Sex and speech and language therapy frequency

Male participants’ best overall language [13.59 points (95% CI 4.3 to 22.88 points) on the WAB-AQ (21 IPD; 2 RCTs)] and functional language gains [0.81 points (95% CI 0.09 to 1.53 points) on the AAT-SSC (6 IPD; 3 RCTs)] were associated with receiving SLT at least 5 or more days weekly. In contrast, females’ highest overall language gains [24.22 points (95% CI 7.73 to 40.71 points) on the WAB-AQ (5 IPD; 2 RCTs)] occurred alongside receiving SLT 3 days weekly, whereas their best functional language [1.01 points (95% CI 0.21 to 1.81 points) on the AAT-SSC (49 IPD; 3 RCTs)] and auditory comprehension gains [8.13 points (95% CI 2.65 to 13.60 points) on the TT-AAT (52 IPD; 5 RCTs)] were associated with receiving SLT 4 days weekly. The males’ best auditory comprehension gains [5.06 points (95% CI 1.41 to 8.71 points) on the TT-AAT (99 IPD; 8 RCTs)] also occurred alongside receiving SLT 4 or 5 days weekly. For both groups, their highest naming gains (on the BNT) also occurred when SLT was received up to twice weekly [females: 17.05 points, 95% CI 9.47 to 24.64 points (17 IPD; 4 RCT); males: 10.58 points, 95% CI 4.29 to 16.86 points (25 IPD; 4 RCTs)] (see Appendix 30, Table 34, and Appendix 34, Table 41).

Sex and speech and language therapy duration

Male participants’ best gains on overall language ability [16.72 points (95% CI 7.79 to 25.65 points) on the WAB-AQ (26 IPD; 3 RCTs)], naming [11.03 points (95% CI 5.38 to 16.67 points) on the BNT (51 IPD; 4 RCT)] and functional communication [0.67 points (95% CI 0.40 to 0.95 points) on the AAT-SSC (46 IPD; 4 RCT)] were all associated with > 10–20 weeks of SLT. Relative variance was unacceptably high for auditory comprehension (> 50%).

In contrast, female participants made their highest overall language [24.52 points (95% CI 13.22 to 35.81 points) on the WAB-AQ (12 IPD; 2 RCTs)] and auditory comprehension gains [6.97 points (95% CI 0.83 to 13.11 points) on the TT-AAT (63 IPD; 3 RCTs)] with > 20 weeks of SLT. Their functional communication gains were best alongside between 4 and > 20 weeks of SLT [0.97 points (95% CI 0.09 to 1.84 points) on the AAT-SSC (16 IPD; 2 RCTs)]. Relative variance was unacceptably high (> 50%) for auditory comprehension (male group) and naming (female group) (see Appendix 30, Table 34, and Appendix 34, Table 41).

Sex and speech and language therapy intensity

For the female group, SLT for up to 2 hours weekly was associated with the highest gains on overall language ability [18.53 points (95% CI 7.46 to 29.59 points) on the WAB-AQ (37 IPD; 3 RCTs)], auditory comprehension [7.91 points (95% CI 1.82 to 14.00 points) on the TT-AAT (10 IPD; 2 RCTs) based on small numbers] and functional communication [1.15 points (95% CI 0.47 to 1.87 points) on the AAT-SSC (39 IPD; 4 RCTs)]. Their best naming gains occurred in the context of ≤ 2 to 3 hours of SLT weekly [13.48 points (95% CI 4.67 to 22.30 points) on the BNT (38 IPD; 5 RCT)].

In contrast, the male group’s highest gains on overall language [15.13 points (95% CI 7.92 to 22.34 points) on the WAB-AQ (61 IPD; 3 RCTs)] and auditory comprehension [7.63 points (95% CI 3.77 to 11.48 points) on the TT-AAT (91 IPD; 6 RCTs)] were associated with > 9 hours of SLT weekly. Male participants’ best functional communication [0.65 points (95% CI 0.40 to 0.89 points) on the AAT-SSC (97 IPD; 5 RCTs)] and naming gains [15.54 points (95% CI 6.94 to 24.14 points) on the BNT (10 IPD; 2 RCT)] were observed alongside between 2 and > 9 hours of SLT and up to 2 hours SLT weekly, respectively (see Appendix 30, Table 34, and Appendix 34, Table 41).

Sex and speech and language therapy dosage

For both female and male participants, the best gains on overall language ability (measured on the WAB-AQ) were associated with at least 20–50 hours of SLT [females: 24.37 points, 95% CI 12.22 to 36.52 points (13 IPD; 2 RCTs); males: 15.61 points, 95% CI 6.23 to 25.00 points (18 IPD; 4 RCTs)], although IPD and RCT numbers were low.

Functional communication gains (measured on the AAT-SSC) were best for the male group alongside > 50 hours of SLT [0.70 points, 95% CI 0.48 to 0.91 points (93 IPD; 6 RCT)], whereas the female group’s best gains occurred with 14–20 hours of SLT [1.59 points, 95% CI 0.57 to 2.61 points (4 IPD; 2 RCTs)], but this was based on very low IPD and RCT numbers. The next highest gain on functional communication for the female group was in the context of 20–50 hours of SLT [0.90 points (95% CI 0.38 to 1.42 points) on the AAT-SSC (43 IPD; 8 RCTs)]. Relative variance for both groups on the naming analysis was unacceptably high (> 50%) (see Appendix 30, Table 34, and Appendix 34, Table 41).

Summary

Optimal language gains for younger and older participants were generally associated with similar levels of SLT frequency and dosage. Younger participants’ best overall language and auditory comprehension gains were associated with high-intensity SLT (> 9 hours weekly). Although older participants’ best auditory comprehension gains were also associated with high-intensity SLT, their highest overall language, naming and functional communication gains were associated with lower-intensity SLT (≤ 2 hours weekly).

Generally, when differences were noted, participants in the early stages of aphasia recovery made their best overall language gains in the context of SLT that was less intensive and at a lower dosage than participants with long-standing aphasia (late group), who made their greatest gains alongside SLT that was at a slightly higher intensity and dosage.

The analysis of the mild–moderate group’s language gains was limited by possible ceiling effects, although the group’s best overall language and naming gains were associated with high intensity SLT (> 9 hours weekly). In contrast, the moderate–severe group’s best gains on these measures were associated with less intensive SLT interventions (3–4 hours and up to 2 hours weekly, respectively).

Male participants’ highest language gains were, when differences were observed, typically associated with SLT that was more frequent and intensive than the SLT regimens associated with the female participants’ best language gains. The subgroup analyses were exploratory and, in some cases, based on small IPD and RCT numbers. The findings highlight some possible associations between specific participant subgroups’ best language gains and SLT frequency, duration, intensity and dosage worthy of consideration in future research.