As population aging continues to become an irreversible global trend, the prevalence of dementia is also expected to increase rapidly. The global prevalence of dementia in older adults is projected to double every 20 years, reaching 58 million in 2020, an anticipated 82 million in 2030, and 150 million in 2050 [1]. The financial cost of dementia was already substantial at US $ 818 billion in 2015 [2]. However, the recent COVID-19 pandemic has amplified the escalating costs of dementia care [3]. The economic impact of dementia extends beyond direct medical and social service expenses, such as treatment, medication, and social welfare, and encompasses indirect costs borne by caregivers and family members of older adults with dementia [4,5]. Caregivers often experience long-term stress, depression, anxiety, burnout, and physical health problems, which can limit their participation in economic activities, thereby amplifying the significant economic burden associated with dementia care [6,7]. The escalating health care burden presents a global social challenge that impacts not only the affected individuals but also families and communities, underscoring the urgent need for comprehensive strategies to address this pressing issue [8].

Although no cure for dementia currently exists, several studies have suggested that preventive interventions in the preclinical and prodromal stages can delay its onset and improve cognitive function by targeting modifiable risk factors [6,9]. The preclinical stage represents individuals who, despite not showing overt clinical signs of cognitive decline, have underlying dementia pathology. Meanwhile, those in the prodromal stage display evidence of clinical decline, demonstrated by subtle changes in cognition and short-term memory loss [10,11]. These stages have become focal points of recent research. Typically, the progression starts with normal cognition, transition into subjective cognitive decline (SCD)—a decrease in cognitive ability that is subjectively perceived compared to prior normal status but irrelevant to objective cognitive test results [12]—and eventually evolves into mild cognitive impairment (MCI), a condition characterized by a noticeable decline in cognitive abilities that does not interfere with daily functioning but increases the risk of Alzheimer disease or other types of dementia [13-15]. This transitional state of MCI poses a relatively high risk of progression to dementia, with some studies highlighting an estimated annual progression rate of approximately 10% [15-18]. However, not all cases of MCI inevitably progress to dementia [19]. The rate of return to normal cognition from MCI varies across studies, but one meta-analysis reports that approximately 24% of individuals with MCI revert to objectively normal cognition [20].

Recently, mild behavioral impairment (MBI), a neuropsychological syndrome that typically emerges later in life and can manifest across the entire predementia spectrum, has been introduced as a precursor to cognitive decline and dementia [21]. Prior to the development and implementation of preventive and supportive interventions for at-risk populations, it is essential to thoroughly understand MBI and its related factors that can influence multidimensional aspects of health in older adults.

According to the latest diagnostic guidelines published by the Alzheimer’s Association International Society to Advance Alzheimer’s Research and Treatment, MBI is characterized by behavioral and personality changes persisting for at least 6 months from the initial onset [22]. These changes, including reduced motivation, impaired emotional regulation, deficiency in impulse control, and inappropriate social behavior, minimally impact interpersonal relationships and workplace performance [23]. Evidence suggests that older adults with SCD who experience MBI are more likely to develop dementia [23]. Moreover, when MBI is accompanied by functional deterioration in daily life, it can serve as a neuropsychiatric symptom and prognostic marker of dementia [21,24]. Therefore, exploring the health outcomes of MBI has significant implications for dementia prevention and prediction of its progression.

Since the diagnostic criteria for MBI were first introduced in 2003 [25,26], MBI has been studied over the past two decades as a predictor and prognostic marker of cognitive impairment and dementia [23,27]. During this period, significant strides were made toward the conceptual understanding of MBI and the development of tailored diagnostic tools offering consistent and reliable means of assessing MBI, such as the Neuropsychiatric Inventory Questionnaire (NPI-Q) and the MBI Checklist [28-30]. The MBI Checklist was validated in comparison with the NPI-Q [31]. Furthermore, diverse methodologies have been employed in MBI research, including family interviews [32], neuropsychological tests [33], and imaging and cerebrospinal fluid diagnostic tests to identify MBI [34]. Several studies have also scrutinized differences in MBI manifestations according to sociodemographic characteristics [30,35] and have examined correlations between biomarkers [36], specific diseases, and MBI [37] as well as the impact of MBI on the progression from MCI to dementia [33,38].

However, as MBI is a relatively recent neurobehavioral concept, the literature lacks a comprehensive review addressing the correlates of MBI in older adults, apart from one meta-analysis on pathological and genetic relationships with MBI prevalence [39]. Given the potential insights into predicting and preventing dementia and assessing the risk of transition to this condition, a thorough review of the physiological, psychological, and social factors associated with the development and progression of MBI, as well as their influence on the relationship between MBI and other health outcomes, is crucial. Therefore, this scoping review aims to provide an overview of MBI and its correlates among older adults. Mapping evidence of factors correlated with MBI will guide the development of targeted preventative and supportive interventions for at-risk populations, laying the groundwork for interventions to promote preventive measures and improve self-management. This will also provide valuable insights for health care providers, enabling them to facilitate awareness and early detection of MBI. This, in turn, can lead to improved patient care and health outcomes. Furthermore, it underscores the importance of addressing behavioral symptoms later in life, and it advocates for targeted patient-centered clinical intervention and nursing care for older adults. The specific research questions are as follows:

An exploratory search was conducted in July 2023, and a comprehensive search strategy was formulated based on the preliminary results. We reviewed studies on MCI and SCD in older adults in the exploratory search and recognized the difficulty in detecting early SCD without substantial empirical data in individuals diagnosed with normal cognition at the study’s inception. Therefore, as noted in the Methods section, we broadened our review scope to include studies of older adults across the spectrum from normal cognition to MCI, refining our search strategy with a librarian's assistance. Iterative refinements to the scoping review protocol and formalization of methods were completed. A subsequent search is scheduled for May 2024, with the objective of submitting the results for publication in peer-reviewed journals.