TyG Index and Cognitive Decline in Non-diabetic Elderly: Evidence from CLHLS 2014-2018

Objective The relationship between insulin resistance (IR) and susceptibility to cognitive decline remains unclear, with conflicting research findings. This nationwide retrospective analysis sought to examine the relationship between cognitive impairment and the triglyceride-glucose (TyG) index, a surrogate marker for IR, among older Chinese individuals without diabetes. Methods Data analysis was conducted using information derived from the 2014–2018 cohort of the Chinese Longitudinal Healthy Longevity Survey (CLHLS), comprising 988 non-diabetic adults whose mean age was 79.78 years (SD = 9.21). The study population included participants, 572 were male (57.89%) and 416 were female (42.11%). The Mini-Mental State Examination (MMSE) was employed to evaluate cognitive function. Multivariate Cox proportional hazards models were utilized to assess the association between the TyG index and the likelihood of cognitive impairment. To investigate potential threshold effects, a two-piecewise Cox regression approach was implemented. Furthermore, the study incorporated interaction and stratified analyses, taking into account factors such as age, gender, marital status, exercise habits, smoking, and alcohol consumption. Results After a 4-year follow-up period, 201 participants (20.3%) developed cognitive impairment, despite having normal cognition at baseline. Controlling for relevant variables, the multivariate Cox regression analysis did not reveal a statistically meaningful link between cognitive decline and the TyG score (HR = 0.77, 95% CI: 0.56–1.06, P = 0.106). However, smoothing plots suggested that the relationship between cognitive impairment and the TyG index was non-linear, with a turning point identified at 7.57. Above this inflection point, a negative association was observed (HR = 0.67, 95% CI: 0.50–0.91, P = 0.009), whereas no notable association was found below it (P = 0.75). Conclusions Our research uncovers a nuanced, non-linear association linking the TyG index to cognitive decline among elderly individuals without diabetes. These results offer valuable insights with implications for informing public health strategies and policy development.