Due to the aging of the global population, the number of people suffering from cognitive decline is increasing.1,2 Cognitive decline seriously affects the independence and quality of life of older people3,4 and is one of the main causes of disability.5 In addition, it is the main symptom of dementia, for which there is currently no effective treatment.6 Cognitive decline is a global public health problem that impedes the development of healthy aging and leads to heavy care and economic burdens among families and society.7 Identifying factors that are associated with cognitive decline is of great significance for developing effective management strategies.

The prevalence of chronic pain among older people was as high as 57.3 %.8 In the International Classification of Diseases (ICD-11), chronic pain is considered a multifactorial phenomenon that involves biological (nociception), psychological (pain cognition, behavior, emotion) and social (social support) factors.9 Currently, multiple studies have shown that chronic pain is closely correlated with worse cognition, such as memory, attention, information processing ability and executive function.10, 11, 12, 13 However, the conclusions were not consistent, and chronic pain with different characteristics may have significant effects on different cognitive domains. In addition, these studies assessed only the nociception dimension of chronic pain and neglected the characteristics of psychological and social aspects and their complex interactions. All of these factors, such as pain catastrophizing, reduced physical activity, stress, depression, and anxiety, which often accompany chronic pain, have been shown to be significant factors influencing cognitive function.14, 15, 16, 17, 18, 19 Presently, treatments for chronic pain in the older population include pharmacological, physical, cognitive, and behavioral therapies. Due to differences in the phenotypic characteristics of pain, there is a great heterogeneity in the response of patients to analgesic treatments.20 Comprehensive consideration of multiple dimensions is conducive to accurately identifying the specific characteristics of chronic pain associated with cognitive decline in specific domains, which is of great value for formulating relevant management strategies.

Latent class analysis (LCA) can model multiple latent variables to identify different subgroups, and the characteristics of each subgroup can be displayed intuitively.21,22 There have been studies applying LCA to the classification of chronic pain in patients receiving multimodal inpatient treatment21 and adults with refractory chronic pain.23 However, they only considered pain nociception/pain cognition and psychoemotional factors, and did not analyze the relationship between pain classes and cognitive function.

Consequently, this study aimed to (1) construct an optimal model of latent classes for chronic pain among older individuals through LCA based on perceptual, cognitive, behavioral, emotional and social profiles and (2) explore the association between each class of chronic pain and various domains of cognitive function. This would be helpful to identify the specific characteristics of chronic pain associated with cognitive decline in older adults and to develop corresponding management strategies.