Background

Parts of this report have been adapted with permission from Brady et al.1 © Wolters Kluwer Health Inc.

Aphasia

Of the estimated 10.3 million people worldwide who experience a stroke each year, 3.6 million people (35%2) are likely to have a stroke-related language impairment known as aphasia. Each year, an estimated 35,000 people in the UK experience a newly acquired aphasia, affecting not only their language abilities (ability to speak, understand, read and write words and sentences), but may also affect their ability to use gesture, tell the time, use money and perform simple mathematical calculations. Of those who experience aphasia, 61% continue to have communication problems 1 year later.3 Approximately 350,000 people in the UK are thought to be living with aphasia.4

Impact of aphasia

Aphasia is one of the most common and most devastating long-term consequences of stroke5 and extends beyond the communication domain. Stroke survivors with aphasia have poorer functional recovery (p = 0.007)6 {comprehension deficits, in particular, affect activities of daily living [odds ratio (OR) 5.38, 95% confidence interval (CI) 2.35 to 12.34; p < 0.001]},7 continence (p = 0.003)8 and emotional well-being (r = 0.51; p = 0.001)9 after stroke than stroke survivors without aphasia. People with aphasia receive less pain medication than other stroke surviors.10 Aphasia also negatively affects hospital discharge destination (p = 0.002),6 the likelihood of successful return to work (p = 0.009)11 and self-rated health after stroke.12 These outcomes are despite people with aphasia having more contact with rehabilitation specialists2 and more rehabilitation interventions13 (contributing to the higher cost of care for people with aphasia) than those without.14 In the USA alone, the presence of aphasia at the time of stroke adds US$2.16B, annually, to the cost of acute stroke care.15 The communicative quality of those rehabilitation interactions may, thus, benefit from closer investigation.

Aphasia and psychosocial impacts

Aphasia directly influences a person’s perception of their own identity16,17 isolating the person with the communication impairment from their spouse, family and wider social networks.18,19 Family members have also described feeling isolated.20 Aphasia intensifies social problems more generally associated with a stroke, restricting or altering social activities.21 This leads to fewer friendships and smaller social networks than before the stroke, and than both healthy peers and stroke survivors with preserved language abilities.18,21 With restricted opportunities for social participation, people with aphasia become socially isolated, which severely affects their emotional well-being.19 Spontaneous recovery of language and communication abilities has been thought to be limited beyond the first year after aphasia onset.22 Emerging research has questioned this premise,23 and further evidence indicates that focused therapeutic interventions may provide benefit in later stages after stroke.24–26

Aphasia recovery

Aphasia recovery and participant demographics

Clinical guidelines recommend that people with aphasia are provided with ‘realistic recovery prospects’ following aphasia,27 but, based on current evidence, accurate prognosis is difficult. Although age has been associated with language recovery, the nature of that interaction remains unclear.3,13,28,29 Patient sex has been reported by some to be linked to the incidence of aphasia13 and initial aphasia profile (but not recovery3,28), although several large, well-controlled studies found no evidence of this effect.2,3,30 Conducting a large-scale investigation of aphasia after stroke has often required compromise, with language data based on a single item in a global stroke severity scale,2,3,29 and, in some cases, restricted to one aspect of language use.3 Details on the ability to speak, understand, read, write and participate in everyday communication activities are often unavailable in these tools, thereby limiting our clinical interpretation of aphasia impact and recovery.

The contribution that socioeconomic status and educational background make to recovery may also be relevant, but the interconnectedness of these factors with cognition and performance on measures of language ability makes this a difficult concept to untangle.3,31–33 The incidence of aphasia is similar among monolingual and bilingual stroke survivors, although it has been suggested that bilinguals experience a milder aphasia.34 However, studies using imaging data found that bilinguals’ performances on a detailed language assessment protocol were worse than monolinguals’ performances.35 Social support prior to and following a stroke may also positively influence outcome36,37 and, although opportunities to practise functional language use have been shown to decrease as a consequence of aphasia,18 they are also an important factor in aphasia recovery38,39 and research.38

Aphasia recovery and stroke profile

Initial stroke severity13,28 and time since stroke may be important factors in language recovery, the latter specifically in relation to the acceptability of high-intensity therapy.40,41 There is growing evidence that the site and size of stroke lesion (although perhaps not structural connectivity) are indicators of language recovery.31,42 Stroke-related problems, including depression and cognition, vision and hearing impairments, are also thought to be important to language recovery and rehabilitation.43–45 Others suggest that the initial aphasia profile (i.e. severity, domains involved, abilities retained) may predict the pattern of language recovery.3,28,31 Concomitant stroke-related speech disorders, such as dysarthria (a motor speech disorder) and apraxia (disordered planning of movement to produce speech), may also affect initial functional outcomes and recovery.46

Speech and language therapy for people with aphasia after stroke

Effective management and rehabilitation of aphasia is vital.41 People with aphasia experience significant benefits on measures of functional communication, understanding and spoken language after stroke following speech and language therapy (SLT) than those who do not receive therapy.41 SLT for people with aphasia is highly complex47 and typically tailored to a heterogeneous group (Figure 1).

FIGURE 1 Speech and language therapy for aphasia. (Figure not reproduced here; see the original article.)

Therapy activities may be delivered by a range of therapist-trained providers (therapists, volunteers or family members).41 There is no indication that individual, group or self-managed therapy delivery approaches using personalised computer software, for example, affect SLT benefits for people with aphasia.41 Therapy interventions may target a range of language domains (e.g. spoken language, auditory comprehension, writing) or aim to educate carers and staff to maximise communicative effectiveness through conversational support for the person with aphasia. Interventions may adopt any one or more of several theoretical approaches (e.g. melodic intonation or functional, semantic, phonological or multimodal therapy), while the optimum intervention regimen (timing, intensity, frequency, duration and dosage) remains uncertain.22,41,48,49

Regimen

Early stroke rehabilitation has been advocated50 to maximise the period of neuronal reorganisation in the brain subsequent to the stroke lesion,51 in a context of enhanced rehabilitation environments and stimulation.52,53 Recent randomised controlled trials (RCTs) of SLT interventions have recruited within clinically relevant timelines (days to weeks after stroke)54–56 with mixed results, whereas others have demonstrated benefits among more chronic participants.57 The optimal timing of language rehabilitation for people with aphasia after stroke continues to be uncertain, and evidence of the most effective SLT intervention regimen, based on therapy frequency (number of therapy sessions weekly), duration (start to end of therapy intervention), intensity (number of hours weekly) or dosage (total hours) provided, is also unclear.

Intensive SLT intervention has been found to benefit functional communication, written language and severity of aphasia, but significantly more people withdrew from (dropouts for any reason p = 0.005), or declined to continue with (non-adherence p < 0.00001), intensive therapy than less intensive therapy.41 Interestingly, differential withdrawal and non-adherence rates and the language recovery benefits were observed only among people within 3 months of their stroke. Thus, therapy regimen and participant factors may be important independent and interdependent factors in the effectiveness of and tolerance to SLT for aphasia after stroke.

Clinical guideline recommendations

UK and international clinical guidelines on aphasia after stroke highlight the paucity of guidance to support therapists’ provision of aphasia rehabilitation interventions.58 Evidence-based stroke clinical guidelines rarely offer specific therapy approach, regimen or mode of delivery recommendations, in contrast to movement rehabilitation recommendations for strength and fitness training, orthoses, electric stimulation and more.59–61

Early62,63 and high-intensity SLT64 may be effective, but these historic reviews of SLT for aphasia were limited in their design (time-bound, English language only, small number of studies included, summary data analysis only). The Cochrane review (57 RCTs, n = 3002 participants) found that the potential benefit of high-intensity SLT was confounded by a significantly higher dropout rate from intensive SLT groups.41 Tailoring to the individual is considered essential,65 but is based on best practice recommendation. High-quality information from large-scale research projects does not currently exist to guide therapists’ choice of an effective therapeutic approach best suited to a specific patient with aphasia (and their families).

Data sets capturing a large number of people with aphasia after stroke are typically based on single-centre data with relatively small numbers of individual participant data (IPD). In studies for which larger numbers of IPD are available (n > 200), the quality of information on language outcomes is often restricted, informed by a language data item on a generic stroke scale or screening tool gathered by non-language specialists2,3,29 and lacking a full description across a range of language skills.

Availability of speech and language therapy for people with aphasia

Information on clinical services for people with aphasia after stroke is difficult to gather. A 2003 UK survey found that therapists providing adult services reported that only one-quarter of their time was spent on aphasia. Of available SLT time for aphasia, just 5% was spent on interventions with an intensity of > 3 hours weekly.66 Half of SLT time was invested in interventions at an intensity of < 3 hours weekly.66 An earlier survey reported in 2000 indicated that the average total duration of SLT interventions for people with aphasia ranged from one to five sessions in the UK and Australia.67 North American SLT interventions ranged from 16 to 20 sessions.67 Since then, hospital-based SLT in Australia may have increased, with a 2009 survey describing typical intervention intensity of 4 hours weekly (2 hours weekly in acute settings).68 Information about the SLT received by 278 people with aphasia from across the UK prior to their involvement in the Big Clinical and cost-effectiveness of aphasia computer treatment versus usual stimulation or attention control long term post-stroke (Big CACTUS) trial69 showed that, in the first 3 months from the index stroke and pre recruitment, participants had received a total dosage of 11 hours of SLT, delivered at an intensity of approximately 1 hour weekly. People who were ≥ 5 years after the index stroke received a total dosage of 2.75 hours over the preceding 3-month period, delivered at an intensity of 45 minutes monthly,69 even lower than the 1 hour weekly reported for people with aphasia in the Australian community.68

National audits, although capturing information on access to clinical services, rarely distinguish between time spent with a speech and language therapist for dysphagia (swallowing problems) and aphasia.2 The Sentinel Stroke National Audit Programme (SSNAP) does, however, highlight the lack of resources for SLT services, a sentiment echoed by therapists.70 The 2016–17 SSNAP data71 highlighted stroke specialist services with no speech and language therapist, whereas others had a very limited service (one or less full-time equivalent therapist), leaving service provision for aphasia vulnerable should a therapist be on leave, move post or retire.

There is some suggestion, however, that standard SLT services may be changing in some centres. Usual care provided to participants with aphasia in a recent Australian Phase III trial72 found that the usual care arm provided early SLT intervention to 81% of participants, compared with just 12% in the Phase II trial.56 Similarly, the Phase III trial72 usual care participants received more frequent SLT, and a SLT dosage of 9.5 hours over the first 7 weeks (approximate intensity of 1.5 hours of SLT weekly), compared with an average intensity of 14 minutes of SLT weekly in the Phase II trial.56 Although the triallists acknowledge that this could be related to the sites simply being part of a trial (the observer effect), it may also suggest a shift in usual SLT interventions over time in those centres.56,72

Aphasia: a research priority

Aphasia intervention research was identified twice in the shared top 10 research priorities by stroke survivors, family members and health-care professionals in the 2011 James Lind Alliance Priority Setting Partnership.73 Effective aphasia rehabilitation and support interventions for people with aphasia and their families were agreed to be urgent unmet research needs.73 More recently, the Royal College of Speech and Language Therapists (in the UK) identified aphasia research as a top five research priority topic among their membership.74 Two further priority-setting initiatives for aphasia research also identified the need for clinically relevant information regarding aphasia therapy intervention approaches, timing, intensity, duration, dose of therapy and therapy provider among the research priorities.48,49

Rehabilitation of aphasia after stroke: a research challenge

The recent priority-setting initiatives have highlighted the gaps in evidence informing the delivery of SLT to people with aphasia. Growing recognition of the importance of focused, early rehabilitation after stroke (for example by Bernhardt et al.75) has occurred in parallel with increasingly constrained NHS therapy budgets. Prognostic indicators may inform the development of predictive models that acknowledge the existence of parallel spontaneous recovery alongside the benefits of early intervention and brain plasticity.51 The diversity among people with aphasia and the range of therapeutic interventions have led some to question whether or not large RCTs of SLT for aphasia is the optimal approach to gaining insights into what works best and for whom.76

Complex SLT interventions (see Figure 1) may be optimised, and specific patient subgroups may benefit from particular SLT interventions. Large-scale investigations of SLT for aphasia are possible and worthwhile.25,26,55–57,72 International collaboration in this field may be further challenged by the difference in languages across centres and the lack of non-English-language aphasia assessment measures. However, examining the impact of the many permutations of a complex intervention such as SLT on a complex population, which varies by participant, aphasia and stroke profile, would need decades of large, logistically challenging and costly RCTs. Much insight may be gained to inform the design of clinical services and future aphasia research by exploring existing aphasia research data sets.

Synthesising pre-existing aphasia research data

Data synthesis and secondary analysis of large, aphasia-specific data sets has informed our understanding of SLT for aphasia after stroke. Pooling of group-level summary (aggregated) data demonstrated the effectiveness of SLT for aphasia across language domains. It also identified a possible interaction between the SLT regimen and timing of therapy after stroke, and also methodologically in relation to the choice of attention control interventions.38,41 Meta-analysis has provided a cost-effective way to inform our understanding of aphasia recovery and rehabilitation before moving forward with costlier RCTs. Such an approach, however, also has limitations.

Traditional meta-analysis makes paired comparisons (therapy A vs. therapy B), but does not easily permit a comparison of therapy A versus B versus C versus D. Clinically, SLT interventions are tailored to individual patients’ degrees of language impairment across modalities, attention or levels of fatigue. Group-level summary statistics prevent examination of the influence of participant-level covariates (e.g. age, time since stroke, aphasia severity or sex) on treatment effects.

Secondary analysis of IPD ensures that individuals (their aphasia and stroke profile, recovery and, when relevant, tailored therapy approach) would be analysed in the context of their individual data set, and not aggregated and averaged across a highly heterogeneous group. A collaborative, international approach to data-sharing and retrieval of published and unpublished data sets would support the development of a substantive database to explore key clinical and research questions, such as the patterns and predictors of language recovery, optimum SLT approaches for aphasia rehabilitation and treatment effect modifiers, benefiting researchers, therapists and people with aphasia.

Aims

The aims were to explore the contribution that individual characteristics (including stroke and aphasia profiles) and intervention components make to the natural history of recovery and rehabilitation of people with aphasia following stroke, and to inform future research design by utilising pre-existing aphasia data to explore the following:

• the natural history of language recovery
• the patient, aphasia, stroke and environmental characteristics that are linked to good language recovery
• the components of effective therapy interventions.

Research questions

The research questions are in Box 1.

• What is the pattern of language recovery following stroke-related aphasia?
  • What is the natural history of language recovery?
  • When is language recovery most likely to occur?
  • Which components of language are most/least likely to recover (overall language ability, spoken language, auditory comprehension, reading comprehension and writing)?
  • Does this vary by language?
• What are the predictors of language recovery outcomes following aphasia in relation to:
  • Aphasia profile (the degree to which overall language ability, auditory comprehension, spoken language, reading comprehension and writing have each been affected in one or more languages)?
  • Individual characteristics (age, education, cognition, mono- or multilingual)?
  • Rehabilitation environment (social support, socioeconomic demographics, ethnicity)?
  • Stroke profile (severity, lesion type, size, location)?
• What are the components of effective aphasia rehabilitation interventions in relation to:
  • Timing of intervention?
  • Frequency, duration, intensity and dose of intervention?
  • Repetition and adherence to home-based therapy tasks?
  • Functional relevance and theoretical approach?
• Are some interventions (or intervention components) more beneficial for some patient subgroups (individual, stroke or aphasia characteristics) than others?