Possibility of Age and Prior Psychiatric Illnesses Affecting the Study Design on Cognitive Dysfunction, Psychiatric Distress, and Functional Decline After SARS-CoV-2 Infection

To the Editor:

The research paper by Vannorsdall et al.¹ was quite interesting in that the authors attempted to prospectively analyze the cognitive abilities, mental health symptoms, and functioning at approximately 4 months after the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The study does take a different approach compared to the conventional COVID-19 studies in that it compared the well-being of the non-intensive care unit (ICU) versus the post-ICU patients.

One of the most noticeable characteristics from this study is that there seems to be a slight disparity with regards to the mean age between the non-ICU and post-ICU patients. The post-ICU patients seem to be older (mean 58 years) than the non-ICU patients (mean 49.5 years). This study further shows the possible association between age and the cognitive function and mental health functions of the post-ICU patients, which seems to be lower in all aspects than that of the non-ICU patients except the Oral Trail Making Test Part B. Studies indicate that with increasing age, there will be an accelerated rate of neuronal dysfunction, neuronal loss, and cognitive decline, with many persons developing cognitive impairments.² Furthermore, since more number of older patients show severe SARS-CoV-2 disease manifestations, they are more often admitted to ICUs.³ This could be one of the main reasons for the association of decreased cognitive and mental functions to post-ICU patents compared to non-ICU patients.

The authors used the Quick Dementia Rating Scale (QDRS) for the measurement of mental health and functioning. But in truth, the scale focuses on dementia and cognitive ability rather than a measure of mental health and functioning, so it would have been more appropriate to use the QDRS scale for measuring cognitive ability.⁴ Using QDRS appropriately as a test for cognitive function would definitely yield more value. The authors themselves mentioned in the Materials and Methods section that the QDRS scale would be used for analyzing the “10 domains of cognition, mood, and daily functioning”. Therefore, the functional significance of the QDRS could have been better apprised and used in the study to provide more accurate results.

In the result analysis section of mental ability and functioning, we see a different turn of events where one can notice that in this scenario, the post-ICU patients scored less on three scales including Patient Health Questionnaire-9, Generalized Anxiety Disorder-7, and QDRS than the non-ICU patients, making the mental health disorder less severe in post-ICU patients versus non-ICU patients. Such findings truly provide us with more in-depth analyses of the results.

Since the investigators did not exclude participants with previous cases of cognitive impairment, mental health issues, or other psychiatric and/or psychological illnesses, one cannot confirm whether certain candidates had a prior diagnosis of the same. Studies have indicated that people with mental illnesses are more prone to having comorbidities, and hence a more severe case of SARS-CoV-2 infection and need for hospitalization.⁵ It is entirely possible that some or several participants from the post-ICU patients group had cognitive impairments and/or mental health illnesses which would have inadvertently tainted the study population and hence possibly even the result analysis. Since the study had no well-defined inclusion or exclusion criteria, there is no way to know whether any patient had psychiatric or psychological comorbidities prior to the SARS-CoV-2 infection.

Appropriate questionnaires for the right function and a more well-defined age-based categorization of the patients could prove to be more beneficial for result analysis of the study findings. Especially having an age-matched study population will give us adequate results. Having a proper exclusion and inclusion criteria while taking into consideration the factors being studied in the research, will give a better study population.