COVID-19 has been associated with cognitive impairments, particularly in memory performance (Guo et al., 2022). Given that associative memory typically declines earlier than item memory in conditions such as mild cognitive impairment (Chen & Chang, 2016), it remains an open question whether COVID-19 differentially affects item and associative memory. Furthermore, it is unclear whether such effects are specific to verbal or non-verbal material. To investigate these questions, Weinerova et al. (2024) recruited participants via long-COVID Facebook groups and clinical settings. They reported a significant detrimental effect of COVID-19 status on long-term memory performance across tasks. However, they did not find evidence for their preregistered hypothesis of an interaction between COVID-19 status and either memory type (item vs. associative) or stimulus type (verbal vs. non-verbal).

 

In the Stage 1 report, the authors preregistered a Bayes Factor threshold of 6 as the criterion for supporting the alternative hypothesis. All planned analyses were preregistered, incorporating both frequentist methods (to replicate Guo et al., 2022) and Bayesian ANCOVA (to test the preregistered hypotheses). As data collection had been completed at the time of Stage 1 submission, we assigned a Level 3 bias control to the Stage 1 report.

 

In the Stage 2 report, the authors confirmed a general negative impact of COVID-19 on long-term memory accuracy. Using frequentist ANCOVA, they successfully replicated Guo et al. (2022)’s findings of reduced accuracy in verbal item and non-verbal associative memory among individuals with prior COVID-19 infection. However, they did not replicate the previously observed effect on reaction times. The Bayesian ANCOVA analyses did not reach the preregistered evidential threshold (BF > 6). Verbal associative memory, which was not part of the original replication attempt, also showed reduced accuracy in individuals with prior infection. In contrast, performance on non-verbal item memory tasks showed a ceiling effect, possibly due to methodological differences from Guo et al. (2022). Across all four memory tasks, the authors found robust evidence for decreased accuracy associated with COVID-19 status but no effect on reaction times.

 

Contrary to their hypotheses, models that included interactions between COVID-19 status and either memory type or stimulus type were less likely than the null model, suggesting a general, rather than specific, detrimental effect of COVID-19 on long-term memory.

 

Analyses of vaccination status yielded inconclusive results, likely due to limited sample size and uncertainty in participants' self-reports of vaccination timing relative to infection. The question of whether vaccination has protective effects on cognition remains unresolved and merits further investigation. The authors also reported tentative exploratory findings, such as a potential association between longer time since infection and slower reaction times in verbal item memory tasks. These observations require confirmation in future studies.

 

Overall, the study makes a valuable contribution by replicating prior findings and extending them to suggest a broad impairment of long-term memory associated with COVID-19.

 

The Stage 2 report was reviewed by the same three reviewers who had evaluated the Stage 1 submission. All reviewers agreed that the authors had addressed prior comments and had adhered to the preregistered methodology and analysis plan. As in the Stage 1 evaluation, we note the potential for selection bias introduced by recruiting participants via long-COVID Facebook groups. Individuals with post-infection cognitive complaints may have been more likely to volunteer, limiting generalizability to the broader SARS-CoV-2-infected population. This and other limitations are clearly acknowledged in the Discussion section of the Stage 2 manuscript. The recommender judged that the manuscript met all Stage 2 criteria for recommendation.

 

URL to the preregistered Stage 1 protocol: https://osf.io/tjs5u
 
Level of bias control achieved: Level 3. At least some data/evidence that was used to the answer the research question had been accessed by the authors prior to in-principle acceptance (e.g. downloaded or otherwise received), but the authors certify that they had not yet observed ANY part of the data/evidence.
 
List of eligible PCI RR-friendly journals:
 

1. Chen, P.-C., & Chang, Y.-L. (2016, May). Associative memory and underlying brain correlates in older adults with mild cognitive impairment. Neuropsychologia, 85, 216–225. https://doi.org/10.1016/j.neuropsychologia.2016.03.032

 

2. Guo, P., Benito Ballesteros, A., Yeung, S. P., Liu, R., Saha, A., Curtis, L., ... Cheke, L. G. (2022b). COVCOG 2: Cognitive and memory deficits in long COVID: A second publication from the COVID and Cognition Study. Frontiers in Aging Neuroscience, 14, 804937. https://doi.org/10.3389/fnagi.2022.804937

 

3. Weinerova, J., Yeung, S., Guo, P., Yau, A., Horne, C., Ghinn, M., Curtis, L., Adlard, F., Bhagat, V., Zhang, S., Kaser, M., Bozic, M., Schluppeck, D., Reid, A., Tibon, R., & Cheke, L. (2025). Changes in memory function in adults following SARS-CoV-2 infection: Findings from the Covid and Cognition online study [Stage 2]. Acceptance of Version 1 by Peer Community in Registered Reports. https://osf.io/q5vu2?view_only=228165eb161d490b945ca019143ba98c

COVID-19 has been suspected to have long-lasting effects on cognitive function. The SARS-CoV-2 virus may enter the central nervous system (Frontera et al., 2020; Miners, Kehoe, & Love, 2020), explaining the observed detrimental effects of COVID-19 on verbal planning and reasoning (Hampshire et al., 2021; Wild et al., 2021), executive function (Hadad et al., 2022), and long-term memory (Guo et al., 2022). In particular, Guo et al. (2022) used verbal item recognition and non-verbal associative memory tasks. Weinerova et al. (2024), in the current study, propose to conduct a replication of Guo et al. (2022), but specifically, to disentangle the effect of COVID-19 infection status on both memory type (item vs. associative) and stimulus modality (verbal vs. non-verbal). Furthermore, Weinerova et al. (2024) propose to analyze cognitive function based on vaccination status before infection to provide a critical test of the potential protective effects of vaccination on cognitive function.

Data collection has been completed with 325 participants after exclusion criteria were applied (COVID group N = 232, No COVID group N = 93). Simulations assuming an effect size observed in Guo et al. (2022), a Bayesian t-test comparing the groups, and a Bayes Factor of 6 indicated that N = 320 is sufficient to detect an effect on 79% of simulations. The main analyses will be conducted using a Bayesian ANCOVA that allows for the inclusion of control variables such as age, sex, country, and education level. Both accuracy and reaction times from the item and associative recognition tasks will be analyzed as the dependent variables. In one analysis, vaccination status will be included as a between-subjects factor, to understand whether vaccination status at the time of infection influences subsequent cognitive function. 

It is important to note that participants were recruited through long-COVID Facebook groups and clinics. Therefore, the results must be interpreted carefully to avoid generalizing to all COVID-19 infections. The data are part of a larger longitudinal study, and the current pre-registration applies only to the baseline timepoint for a cross-sectional analysis. The remaining longitudinal data collection is ongoing and is not part of the current pre-registration.  

The study plan was refined after one round of review, with input from three external reviewers who all agreed that the proposed study was well-designed and scientifically valid. The recommender then reviewed the revised manuscript and judged that the study met the Stage 1 criteria for in-principle acceptance (IPA).

 

URL to the preregistered Stage 1 protocol: https://osf.io/tjs5u
 
Level of bias control achieved: Level 3. At least some data/evidence that will be used to the answer the research question has been previously accessed by the authors (e.g. downloaded or otherwise received), but the authors certify that they have not yet observed ANY part of the data/evidence.
 
List of eligible PCI RR-friendly journals:

 

 

 

1. Frontera, J., Mainali, S., Fink, E.L. et al. Global Consortium Study of Neurological Dysfunction in COVID-19 (GCS-NeuroCOVID): Study Design and Rationale. Neurocrit Care 33, 25–34 (2020). https://doi.org/10.1007/s12028-020-00995-3

2. Guo, P., Benito Ballesteros, A., Yeung, S. P., Liu, R., Saha, A., Curtis, L., Kaser, M., Haggard, M. P. & Cheke, L. G. (2022). COVCOG 2: Cognitive and Memory Deficits in Long COVID: A Second Publication From the COVID and Cognition Study. Frontiers in Aging Neuroscience. https://doi.org/10.3389/fnagi.2022.804937  

3. Hadad, R., Khoury, J., Stanger, C., Fisher, T., Schneer, S., Ben-Hayun, R., Possin, K., Valcour, V., Aharon-Peretz, J. & Adir, Y. (2022). Cognitive dysfunction following COVID-19 infection. Journal of NeuroVirology, 28(3), 430–437. https://doi.org/10.1007/s13365-022-01079-y  

4. Hampshire, A., Trender, W., Chamberlain, S. R., Jolly, A. E., Grant, J. E., Patrick, F., Mazibuko, N., Williams, S. C., Barnby, J. M., Hellyer, P. & Mehta, M. A. (2021). Cognitive deficits in people who have recovered from COVID-19. EClinicalMedicine, 39, 101044. https://doi.org/10.1016/j.eclinm.2021.101044

5. Miners, S., Kehoe, P. G., & Love, S. (2020). Cognitive impact of COVID-19: looking beyond the short term. Alzheimer's research & therapy, 12, 1-16. https://doi.org/10.1186/s13195-020-00744-w 

 

6. Weinerova, J., Yeung, S., Guo, P., Yau, A., Horne, C., Ghinn, M., Curtis, L., Adlard, F., Bhagat, V., Zhang, S., Kaser, M., Bozic, M., Schluppeck, D., Reid, A., Tibon, R. & Cheke, L. G. (2024). Changes in memory function in adults following SARS-CoV-2 infection: findings from the Covid and Cognition online study. In principle acceptance of Version 2 by Peer Community in Registered Reports. https://osf.io/tjs5u

7. Wild, C. J., Norton, L., Menon, D. K., Ripsman, D. A., Swartz, R. H. & Owen, A. M. (2022). Disentangling the cognitive, physical, and mental health sequelae of COVID-19. Cell Reports Medicine, 3, 100750. https://doi.org/10.1016/j.xcrm.2022.100750