Predicting Cognitive Development in Younger Stroke Patients Using the Oxford Cognitive Screen

Predicting Cognitive Development in Younger Stroke Patients Using the Oxford Cognitive Screen (STROKY)

The purpose of this study is to investigate whether Oxford Cognitive Screen (OCS) can be used as a predictive tool during hospital admission in younger (<65 years) stroke patients, i.e. whether OCS is able to predict the level of cognitive functioning in these patients at 3- and 9-months post-stroke. Secondarily the investigators also want to examine the relationship between OCS scores and the patients' self-report regarding general level of functioning, and if there is a significant development in cognitive level over time by comparing OCS-scores at the different time points. The investigators predict that: a) Baseline OCS-score collected in the sub-acute phase during hospital admission will be helpful in predicting future level of cognitive functioning and level of general functioning: a low score at baseline will be associated with a relatively low score on the supplementary cognitive tests at 3- and 9-months post-stroke and a lower level of general functioning, and vice versa. B) Adding background information to the baseline data of the patients will improve the prediction regarding the future cognitive and general level of functioning. C) At 3- and 9-months post stroke we expect there to be a correlation between OCS-score and the patient's self-report of general functioning, where a low score on OCS will equal self-reports of low general functioning. D) The investigators expect to see significant differences in OCS-scores at different time points indicative of cognitive remission.

One of the fastest ways to assess patients' level of cognitive functioning is by using screening tools, which have a short administration time and can be applied to a broad group of patients, in contrast to a full neuropsychological evaluation. Nevertheless, since the screening tools consist of a range of subtests across cognitive domains, they do allow for making relatively general assumptions for the patient group the investigators examine. Studies with similar purpose have been performed previously, however, they have applied cognitive screening tools developed originally to target other populations than stroke, such as dementias. In contrast, in this study the investigators will use the Oxford Cognitive Screen (OCS), a tool developed specifically to target stroke patients. The investigators have chosen to focus on stroke population of working-age adults, since predicting future levels of cognitive functioning bears a special relevance for this group due to future work life and/or education, and since even a mild cognitive impairment can have far-reaching consequences.

Setting and recruitment:

This study will include approximately 90 stroke patients recruited from the subacute stroke unit at Bispebjerg Hospital and the subacute stroke unit at Glostrup Hospital. The patients will be assessed three times: during their hospitalization, after 3 months and again after 9 months. The project will not impact the rehabilitation of the patients in that the patients will receive standard rehabilitation care during the course of the study.

A research assistant will look over the list of patients hospitalized at the stroke units weekly and will recruit patients that comply with the inclusion and exclusion criteria. At baseline the patients will be tested with OCS either by a research assistant, neuropsychologist or a therapist working at the specific stroke unit, that has received training by a neuropsychologist to perform the testing. The patient will also be asked to fill out Hospital Anxiety and Depression Scale (HADS) and will be asked about the baseline information that are not deductible from the medical journal (see section about baseline measures).

The follow up sessions will take place either in the home address of the patient or at Bispebjerg- or Glostrup Hospital where they will be invited in advance according to their preferences. The subjects will receive a link and QR-code via e-mail a week in advance to the follow-up session to fill out questionnaires described in the section "3- and 9-month measures". At the follow-up sessions they will be interviewed to fill out MDS-HC, tested with OCS and tested with supplementary cognitive tests by a research assistant. If they have not filled out the questionnaires in advance, the research assistant will help them to do so during the test session.

Sample size assessment based on power calculations:

To be able to prove a small effect size (d = 0.15) in the linear regressions the investigators need to include at least 55 patients.

To be able to prove a small effect size (d = 0.15) in the Repeated Measures ANOVA the investigators need to include at least 73 patients.

Because the Correlation analysis is not used to obtain results about the main objective, which is to predict future cognitive level, a possible larger effect size (d = 0.3) is accepted. To prove a minimum of d=0.3, the investigators need at least 82 patients in the final analysis. The investigators choose therefore to include 90 patients, assuming possible dropout.

Plan for missing data:

Missing/Unavailable/Non-reported/ Uninterpretable or considered missing because of data inconsistency: The investigators will primarily use Maximum Likelihood Estimation to make imputations when data is missing.

Out-of-range results: When the investigators identify an outlier, it will be investigated whether there might be an obvious cause that is unrelated to what the investigators are trying to measure. If this is the case, the datapoint will be ruled out, otherwise it will be part of the final analysis and would be considered as natural variation.

Statistical analysis plan describing the analytical principles and statistical techniques to be employed: The investigators plan to perform 6 separate multiple linear regressions. Prognostic variables will be chosen for each multiple linear regression based on their correlation with the specific outcome variable. Significance would be considered achieved at p < .10.

The possible prognostic variables will be the same in all 6 analyses and are as follows:

Age, sex, years of education, type of stroke, location of stroke, NIHSS-score, additional treatment, HADS-scores at baseline, OCS-score at baseline, pre-stroke working situation, housing situation, cohabitant status, alcohol intake, and physical exercise level. Initially, the investigators will perform a correlation analysis between the possible predictors and outcome. Those that correlate significantly with outcome will be used for regression analysis.

The investigators will perform a separate analysis for each outcome variable as follows:

MDS-HC performance-score after 3 months, MDS-HC difficulty-score after 3 months, MDS-HC performance-score after 9 months, MDS-HC difficulty-score after 9 months, scores of the supplementary cognitive tests after 3 months and scores of the supplementary cognitive tests after 9 months.

Repeated measures ANOVA The investigators plan to perform a repeated measures ANOVA to test if the OCS-score changes over time. This analysis will be corrected for influence of depression and anxiety symptoms and fatigue by correcting for HADS-scores and MFI-20-score. If this test proves significant, pairwise comparisons will be done (LSD-t-test). Significance would be considered achieved at p < .05.

Correlational analyses The investigators plan to perform analyses of correlations between MDS-HC- and OCS-scores. One will be done for the variables at 3 months, and one will be done for the variables at 9 months.

The investigators also plan to perform correlational analyses of the OCS-scores and the scores on the supplementary cognitive tests. One will be done for the variables at 3 months, and one will be done for the variables at 9 months. Significance would be considered achieved at p < .05.

To be able to explain results of the latter correlational analyses between OCS-scores and the scores on supplementary tests the investigators want to execute McNemar's test and Kappa measure of agreement. This is to further theorize how the results of the separate subtests in OCS relates to the subtests of the supplementary testing. These analyses will be done for each OCS-subtest matched to the corresponding subtest of the supplementary test battery. Significance in McNemar's test would be considered achieved at p < .05.

Inclusion Criteria:

• Patients must 1) be diagnosed with stroke, 2) have NIHSS on admission ≥ 2, 3) have findings on imaging confirming stroke, 4) be aged ≥ 18 < 65, 5) achieve a score below cutoff in at least one partial assignment measured with OCS, 6) be capable of giving informed consent, 7) is able to communicate confidently in Danish.

Exclusion Criteria:

• Patients will be excluded if they 1) have a premorbid neurological illness that currently affect cognitive functions, 2) are delirious or suspected to be delirious at the time of baseline testing, 3) have a current or previously diagnosed brain tumor, 4) have a comorbid oncological illness that affect brain functions, 5) have reported alcohol abuse, 6) have a comorbid psychiatric disease necessitating treatment simultaneously with admission due to stroke.