Type 2 Diabetes Mellitus (T2DM) is a chronic metabolic disorder characterized by insulin resistance and impaired insulin secretion, leading to persistent hyperglycemia [1]. It is one of the most prevalent non-communicable diseases and a major public health concern, especially in developing countries like India [2]. Chronic hyperglycemia in diabetes is known to cause microvascular and macrovascular complications affecting various organs, including the kidneys, eyes, heart, and nervous system [3,4]. In recent years, increasing attention has been directed toward the impact of diabetes on brain function, as evidence suggests that prolonged hyperglycemia and metabolic dysregulation can adversely affect cognitive performance [5,6].

Cognitive dysfunction in patients with T2DM ranges from mild cognitive impairment to dementia, with deficits commonly observed in attention, memory, executive function, and psychomotor speed [7]. Several mechanisms have been proposed to explain this association, including chronic hyperglycemia, insulin resistance, oxidative stress, advanced glycation end-product formation, and microvascular ischemia [8]. These factors contribute to neuronal damage and cerebral atrophy, which collectively impair cognitive processing. Additionally, comorbid conditions such as hypertension, dyslipidemia, and obesity further accelerate cognitive decline in diabetic individuals [9,10].

Early identification of cognitive impairment in T2DM is crucial, as it can affect treatment adherence, self-care behavior, and overall quality of life [11]. Regular cognitive screening can facilitate timely interventions that may slow or prevent further deterioration [12]. Despite the growing burden of diabetes in India, cognitive evaluation is often overlooked in routine diabetic care, and regional data on the prevalence and correlates of cognitive dysfunction among Indian patients remain limited [13].

The present study was therefore aimed to assess cognitive function among patients with Type 2 Diabetes Mellitus using the Mini-Mental State Examination (MMSE) and to evaluate its association with clinical and biochemical parameters such as age, duration of diabetes, glycaemic control, body mass index, and blood pressure.

This cross-sectional study was conducted at a tertiary care centre over a period of eighteen months, from January 2024 to June 2025. A total of 100 individuals with T2DM were enrolled from the outpatient and inpatient departments of medicine and endocrinology.

Adults aged between 40 and 75 years who had been diagnosed with T2DM for at least one year were included in the study. Patients with Type 1 diabetes, known psychiatric illness, neurological disorders such as stroke or dementia, chronic alcohol use, visual or hearing impairments affecting test performance, or those on medications influencing cognitive function were excluded. A detailed medical history was obtained, followed by a thorough clinical examination to record sociodemographic data, duration of diabetes, educational level, comorbidities, and treatment details.

All participants underwent anthropometric measurements, including height, weight, and BMI. Blood pressure was recorded using a calibrated sphygmomanometer. Fasting and postprandial blood glucose levels and HbA1c, were measured to assess glycaemic control. Laboratory investigations were performed in the hospital’s central laboratory following standard procedures.

Cognitive function was evaluated using the MMSE, a standardized and validated tool for screening cognitive impairment. The test assessed various domains, including orientation, attention, memory, language, and visuospatial ability, with a maximum score of 30. An MMSE score of 27 or above was considered normal, 21–26 indicated mild cognitive impairment, 10–20 denoted moderate impairment, and a score below 10 represented severe cognitive dysfunction. The data collected were analyzed using appropriate statistical tests to determine the relationship between cognitive function and clinical parameters among individuals with Type 2 Diabetes Mellitus.

The study included 100 participants with T2DM, having a mean age of 57.4 ± 8.8 years. Males constituted 54% of the sample, while females accounted for 46%. Regarding educational status, most participants (43%) had completed secondary education, followed by 27% who were graduates or above. The mean duration of diabetes was longest in those within the 5–10 year range (45%), and the mean BMI was 27.2 ± 3.4 kg/m². The mean HbA1c level among participants was 8.0 ± 1.2%, and hypertension was noted in 58% of the study population (Table 1).

Table 1. Sociodemographic and Clinical Profile of Participants (n = 100)

Based on Mini-Mental State Examination (MMSE) scores, 75% of participants demonstrated normal cognitive function, while 25% exhibited varying degrees of impairment. Among those with impairment, mild cognitive dysfunction (scores 21–26) was observed in 22%, and moderate impairment (scores 10–20) in 3%, with no cases of severe impairment. The mean MMSE score for the total sample was 26.7 ± 2.8, indicating that a quarter of the diabetic individuals had subnormal cognitive performance (Table 2).

Table 2. Distribution of Cognitive Function Based on MMSE (n = 100)

Participants with cognitive impairment were older (61.1 ± 7.5 years) and had a longer duration of diabetes (9.5 ± 4.6 years) compared to those without impairment (56.1 ± 8.8 years and 6.4 ± 3.7 years, respectively). The mean HbA1c level was significantly higher in the cognitively impaired group (8.5 ± 1.3%) than in the unimpaired group (7.9 ± 1.1%). Systolic blood pressure was also elevated among impaired individuals (138.4 ± 14.6 mmHg vs. 131.2 ± 12.9 mmHg). Differences in BMI between groups were not statistically significant (Table 3).

Table 3. Comparison of Clinical Parameters Between Participants with and without Cognitive Impairment

Correlation analysis revealed a significant inverse relationship between MMSE scores and several clinical parameters. Increasing age (r = –0.39, p < 0.001), longer diabetes duration (r = –0.36, p = 0.001), and higher HbA1c levels (r = –0.28, p = 0.005) were all associated with lower cognitive scores. Systolic blood pressure showed a weaker but significant negative correlation (r = –0.20, p = 0.048), while BMI was not significantly correlated with cognitive function (Table 4).

Table 4. Correlation Between MMSE Score and Clinical Variables

The present study found that 25% of patients with T2DM had cognitive impairment on the MMSE, a prevalence that falls within the wide range reported in the literature. Systematic reviews and meta-analyses report considerable heterogeneity in prevalence estimates—many studies using screening tools such as the MMSE or MoCA report prevalence’s from roughly 20% up to over 40%, depending on population age, setting and test cut-offs [14,15].

Several prior investigations conducted in India and other settings report similar variability but generally corroborate that a substantial minority of people with T2DM have measurable cognitive deficits. Regional studies from India have reported prevalence’s that vary by study design and cognitive instrument, with some community and clinic-based reports showing prevalence’s above 30% while others report lower figures; differences in age distribution, education, and case-mix likely explain much of this heterogeneity [16,17].

Our observation of significant associations between lower MMSE scores and older age, longer diabetes duration and higher HbA1c aligns with mechanistic and epidemiological evidence linking chronic hyperglycaemia and longer exposure to diabetes with accelerated cognitive decline. Longitudinal and cross-sectional studies have shown that higher HbA1c and poorer glycaemic control are associated with faster memory decline and greater odds of cognitive impairment, although recent literature also highlights complexity — for example, both chronic hyperglycaemia and episodes of hypoglycaemia or overly intensive glycaemic lowering may contribute to risk in different ways. Hypertension and other vascular risk factors likewise amplify risk, consistent with proposed microvascular and neurodegenerative pathways [18-20].

These findings have practical implications for diabetes care: routine cognitive screening (even with a brief instrument such as the MMSE) may be useful in middle-aged and older adults with T2DM to identify those who could benefit from targeted interventions to optimise glycaemic and vascular risk management and to support adherence and self-care. However, the heterogeneity of prior studies and limitations in screening instruments mean that positive screens should prompt more detailed neurocognitive evaluation when feasible. Finally, this study has limitations: the cross-sectional design precludes causal inference, a single-centre tertiary care sample may limit generalisability to community populations, educational and cultural factors can influence MMSE performance and we used only one screening instrument without confirmatory neuropsychological testing or brain imaging, which may both under- and over-estimate true cognitive impairment

The present study demonstrates that a significant proportion of patients with T2DM exhibit cognitive impairment, with lower MMSE scores significantly associated with older age, longer duration of diabetes, higher HbA1c levels, and elevated blood pressure. These findings underscore the growing recognition of diabetes-related cognitive decline as an important but often underdiagnosed complication of chronic hyperglycemia. Routine cognitive screening using simple tools such as the MMSE may facilitate early detection, timely intervention, and better management of at-risk individuals. Comprehensive diabetes care should therefore not only focus on metabolic control but also incorporate cognitive health assessment to improve overall quality of life and treatment adherence among patients with T2DM.

Conflict of Interest: None declared

Acknowledgement: None

Funding: None

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