Cognitive domain-specific impairments and associated risk factors in type 2 diabetes mellitus: a cross-sectional observational study based on neuropsychological assessment from Xiamen, China

Background Type 2 diabetes mellitus (T2DM) is associated with an increased risk of cognitive impairment, yet limited research has been conducted in subtropical regions of China. Objective To examine the characteristics of cognitive impairment and identify the potential risk factors in patients with T2DM in Xiamen. Methods This cross-sectional observational study included 84 patients with T2DM from Zhongshan Hospital Xiamen University. Patients were grouped based on their Montreal Cognitive Assessment (MoCA) scores into a cognitively impaired group (T2DM-CI group, n = 52) and a cognitively normal group (T2DM-NCI group, n = 32). Multivariate logistic regression was used to identify independent risk factors. Results Among the 52 patients in the T2DM-CI group, the most commonly affected cognitive domains were executive function (82.7%), language (75.0%), memory (61.5%), and attention (48.1%), with 59.6% exhibiting impairments in three or more domains. Compared with the T2DM-NCI group, the T2DM-CI group showed poorer performance in most MoCA subdomains—including visuospatial/executive function, language, delayed recall, abstraction, and orientation—as well as in individual cognitive domain tests (all P < 0.05), except for the Clock Drawing Test. Older age (OR = 1.167, 95% CI [1.045–1.303], P = 0.006) and higher lipoprotein (a) levels (OR = 1.109, 95% CI [1.020–1.205], P = 0.015) were independently associated with cognitive impairment in T2DM patients. Conclusion Cognitive impairment in T2DM affects multiple domains, with executive dysfunction most prominent. Age and elevated lipoprotein(a) may increase risk. Routine cognitive screening is warranted, particularly in older patients and those with vascular risk factors.