Introduction

Cancer is a proliferate global health concern, with approximately 20 million new cases diagnosed in 2022 [1]. The foregoing burden of cancer is projected to increase to 35.3 million new cases by 2050, which is a 76.6% increase from the estimated 20 million cases previously estimated in 2022 [2]. This burden is likely to be disproportionately felt in low- and middle-income countries (LMICs), where the majority of new cancer cases occur in the context of low resources [3]. This is significant, as the increase in the burden of cancer comes with a backlash of diverse cancer morbidities such as neuropathies, psychological challenges, and, of recent interest, cognitive problems/cancer-related cognitive impairment (CRCI) [4].

Previously referred to as “chemo brain” due to the presumed effects of chemotherapy as the sole cause [5], CRCI involves objective neuropsychologically tested deficits in patients’ cognitive functions, such as perception, attention, language, thinking, learning and memory, action planning, understanding, reasoning, and problem-solving [6]. According to Boscher et al. [7], these deficits manifest as patients’ subjective reports of cognitive concerns, such as complaining about forgetfulness, being easily distracted, and difficulty finding words. Available evidence suggests that the foregoing cognitive difficulties can occur before, during, and following any systematic cancer treatment [8, 9]. As Janelsins et al. [10] noted, the prevalence rate was estimated to be 30% before treatment, 75% during treatment, and 35% after treatment.

CRCI has been found to significantly impact cancer patients’ quality of life, treatment adherence, and treatment outcomes [10]. Studies have also found that long-term experience of cognitive problems can prevent patients from returning to their occupational function, social activities, and family life following treatment [11]. For example, in a study conducted by Haywood et al. [12], difficulties associated with executing regular activities, relationality, work-related functioning, psychological distress, and socializing challenges were reported to exist among cancer survivors with CRCI. Thus, emphasizing the need for early identification of cognitive impairment and tailoring timely interventions to buffer against the negative impact of both cancer and cancer treatment on the cognitive ability of patients.

Previous studies have assessed CRCI using both self-report measures and neuropsychological tests, which yield perceived cognitive problems and objective cognitive impairments [13]. For example, studies by Lange et al. [14] and Araujo et al. [15] have found perceived cognitive complaints and objective cognitive impairment among non-CNS cancer patients. However, correlations between perceived cognitive problems and objective cognitive impairment have not always been consistent. Some evidence attributes the inconsistency to the fact that perceived cognitive difficulties may be more related to psychological distress rather than impairment in cognition [16]. For example, in a systematic review by Bray et al. [17], 14 out of 44 studies found a small to moderate correlation between self-reported cognitive concerns and neuropsychological test performance among breast cancer patients. In other studies, a small or no association was reported, suggesting that perceived cognitive problems may not always reflect objective cognitive impairments but are more related to psychological state [14, 18, 19]. This is an important consideration in understanding CRCI since patients’ perceptions of cancer impairment are important and they impact quality of life, especially functional ability and activities of daily living. Furthermore, the emerging evidence suggests that self-perceived cognitive problems are one of the strongest predictors of progression to mild cognitive impairment [20, 21].

Given the inconsistencies in the literature on the association between perceived cognitive problems and objective cognitive function, there is a need to assess cancer patients using both self-report measures and neuropsychological tests to avoid underestimation or overestimation of cognitive dysfunction (as recommended by the International Cancer Task Force-ICTF). This can lead to mitigation against the impact of cognitive problems on quality of life (QOL) and functionality in patients with non-central nervous system cancers. More importantly, in the African context where research on this issue has been neglected, it can fill an important knowledge gap that has the potential to directly impact clinical care, particularly in the pre-treatment phase of patients in resource-constrained environments. Based on the emerging evidence from developed countries [22, 23], patients with non-CNS cancer, including breast cancer, colorectal cancer, etc.—even in the pre-treatment phase—self-report on problems related to concentration and attention (i.e., struggling with multitasking), memory (i.e., difficulties with remembering important information) and executive functioning (i.e., some complaining of having difficulties making decisions in daily functioning). This is a significant problem as it can interfere with the decision to start cancer treatment and adherence to the cancer treatment protocol. For this reason, understanding the self-perception of cognitive impact in patients with non-CNS cancers is important, as it may correlate with their objective cognitive functioning. Thus, this study aimed to examine the association between self-perceived cognitive functioning and the performance on an objective neuropsychological test—the mini-Montreal Cognitive Assessment (mini-MoCA), amongst patients with non-CNS cancer from a resource-constrained environment in South Africa. Understanding this association could help validate the use of self-reported assessment as a reliable indicator for further assessment of objective neuropsychological testing in the local context. This could lead to early identification of cognitive impairments and timelier psycho-cognitive interventions, potentially mitigating the impact of cognitive dysfunction on patients’ everyday functioning and overall quality of life.

Materials and methods

Results

Discussion

The main objective of this current study was to determine the association between subjective and objective cognitive function in patients diagnosed with non-CNS cancer in a resource-constrained setting. The study results form part of the literature attempting to reconcile the debate on the inconsistencies between subjective cognitive complaints and objective cognitive function that has predominately been conducted in developed countries. Consistent with existing research [14, 16, 30], the results of this study found a small non-significant association between self-reported cognitive complaints, as measured by symptom endorsement on the PCI and performance on the brief objective neuropsychological test, the mini-MoCA, in this sample of South African patients with non-CNS cancer before treatment.

This finding is not surprising as existing literature from a systematic review and meta-analysis of general population studies by Burmester et al. [31], has revealed small associations between subjective and objective cognition, with limitations in small sample sizes. Similar to our study, previous studies with cancer patients have often been limited by small sample sizes [17], which may underestimate the effect size. However, it is worth noting that our current study effect size (r = 0.22) was considerably larger than that reported in general populations (r = –0.13). This larger effect size could be attributed to the memory sub-domain, which was statistically significant.

Indeed, memory is readily the first symptom of cognitive changes noticed by patients and caregivers leading to higher identification of impairment on objective testing [32]. This is particularly due to deficits in short-term and delayed memory recall, which are more sensitive to early-stage cognitive changes that individuals experience in their daily functioning [33]. Thus, it can be cautiously hypothesized that self-reported cognitive impairment may indicate early underlying cognitive deficits, particularly in memory, among pretreatment cancer patients. However, this hypothesis requires careful exploration in future research. Moreover, the association fell within the small to moderate range, suggesting that PCI might not always correlate with memory (or objective impairment), or it reflects the impact of modifiable factors [32]. This conclusion is supported by a review of 24 studies conducted by Hutchinson et al. [34], which highlighted the inconsistent associations between subjective and objective impairment in studies primarily focused on the correlation between PCI and memory.

Moreover, in this study, just over 40 percent of the participants self-reported cognitive complaints, while close to 64 percent of the sample were found to have objective mild cognitive impairment based on the performance on the mini-MoCA. Among individuals who did not self-report cognitive problems on the PCI, at least 55% were found to be cognitively impaired based on their performance on the mini-MoCA (Table 3). Conversely, about 18% of those who self-reported cognitive impairment on the PCI were found to perform within the cognitively intact range on the MoCA. This could suggest that some patients might be overestimating and underestimating their cognitive function, which is commonly seen in patients with anxiety-depressive symptomatology [35, 36]. It is well reported in affective neuroscience research that emotional state affects cognitive performance and self-perception [36–38]. Previous research has suggested that the non-significance and inconsistent prevalence results could be due to the link between self-reported cognitive complaints and psychological factors such as depression, anxiety, and fatigue rather than underlying neurological fallout [8]. This is perhaps important to consider in interpreting the results since this study did not include the evaluation of the possible influence of depression, anxiety, and fatigue. Some research showed that not only was anxiety and depression high amongst patients with a recent diagnosis and before starting chemotherapy, but that it also had adverse effects on cognition, particularly attention, memory, information processing, and the self-appraisal ability of patients [19, 39, 40]. This factor may contribute to the current study results, but further research specifically investigating the influence of psychological factors is needed since previous research has found non-significant associations. Additionally, some existing research suggests that subjective and objective cognitive impairments might represent distinct constructs that are not well captured by current neuropsychological test batteries [20, 41]. Changes in everyday functioning and daily stressors may not be effectively measured through standardized testing, which could contribute to the inconsistencies observed in studies on subjective and objective cognitive impairment.

This study did not find a significant difference in sex, age, educational status, relationship status, or comorbidities between those who self-endorsed cognitive impairment and those who reported no impairment on the PCI measure. This is consistent with previous research that found no differences in PCI based on the aforementioned characteristics [19, 42–44]. Similarly, the performance on the objective measure, the mini-MoCA, study showed no significant differences in all the variables, except for age. The significant difference in mini-MoCA performance based on age aligns with predominant existing research showing that older cancer patients have a higher risk of cognitive impairment [39, 45, 46]. This can be attributed to age-related neurodegeneration and reduced cognitive plasticity or reserve [47]. In this study, we recruited a patient population younger than 60 years in an attempt to minimize the bias of possible age-related cognitive decline. To note, the sample of patients had a mean age of 43.32 years. The non-significant findings regarding these factors contradict earlier studies by Mandelblatt et al. [45] and Yang et al. [46], which found that the likelihood of impairment was significantly higher among women with lower education levels, those with greater comorbidity, and specific relationship statuses. This earlier research suggests that there may be a link between cognition and sociodemographics, as well as comorbidities. The differing results in this study might be influenced by the homogeneity of the study sample, which consisted of Black African patients from lower socioeconomic backgrounds who had access only to the government healthcare system.

The observed modest correlation, especially the significance in the memory subdomain, along with the notable yet underpowered effect of the global MoCA score, holds considerable importance in a low-resource setting. Thus, the findings underscore the importance of regular cognitive screening, psychosocial assessment, and psychoeducation as part of the early oncology care pathway. This is especially crucial during the acute period following diagnosis and before the initiation of any cancer treatment. It is important since patients frequently report cognitive problems to their primary oncologist but often feel dismissed [48]. The existing evidence suggests that cognitive symptoms can worsen depression-anxiety, while psychological issues can intensify cognitive complaints and dysfunction [48–50]. Therefore, regular screening and early assessments are important for identifying potential vulnerabilities to impairment. Early intervention can help mitigate the severity of cognitive impairment and psychological dysfunction, which can ultimately benefit patients starting chemotherapy and enhance overall treatment compliance.

This study has several limitations that should be acknowledged. Firstly, it is a cross-sectional correlational study, meaning it does not account for changes over time and precludes any form of causation. Secondly, depression, anxiety, and fatigue were not part of the current study analysis. Therefore, further research should investigate the relationship of the study variables over time and consider potential mediating or moderating factors, particularly the role of depression-anxiety symptoms. Thirdly, the participants in this study were recruited purposively, which introduced unavoidable selection bias due to the nature of the study. Additionally, the results are based on data collected from a single treatment facility, limiting the generalizability of the findings. Caution should be exercised when interpreting the results too broadly. Fourth, although the MoCA has been used locally in research and clinical settings, it has not been normed for the local population. To the best of the researcher’s knowledge, the study is one of the first to investigate the association of self-reported cognitive problems and objective cognitive impairment before treatment in this context. A notable strength of this study is the strict inclusion criteria, particularly the control for the influence of chemotherapy and surgery, both of which are independently linked to cognitive impairment [51, 52].