Abstract
Background: Obesity, the global public health burden, is a risk factor for various metabolic and cardiovascular complications and is also known to affect the peripheral and central nervous systems. The electrophysiological test like pattern shift visual evoked potential (PSVEP) can help in evaluating the functional status of the visual conduction pathways. Obese adults were also known to have reduced cognitive ability. Rey-Osterrieth complex figure test (ROCFT) assesses visuospatial ability, visual learning, and memory. Although a number of studies were done to know the effect of obesity on Visual Evoked Potential and cognition, the results were inconsistent and the role of ROCFT in detecting mild cognitive impairment was rarely applied and hence this study was chosen.

Aim and Objectives: This study aimed at assessing the latency and amplitude of PSVEP and ROCFT among normal, overweight, and obese young adults and correlating their BMI with PSVEP and ROCFT scores.

Materials and Methods: After getting institutional Scientific and ethical committee clearance, the analytical cross-sectional study was done among 90 young adults of both genders of age 18–21 years. Written informed consent was obtained from all the participants willing to participate in the study. Participants with a history of hypertension, diabetes, other hormonal disorders, psychiatric illness, chronic medication, and refractive error (without correction) were excluded. Participants were divided into three groups based on Indian-specific body mass index. (BMI) P100, N75, and N145 latency in a millisecond and P100 amplitude in μV of PSVEP were recorded using Neurostim NS4, Medicaid system, Chandigarh, in the research laboratory at the Department of Physiology from 10 AM to 12 PM. ROCFT was scored based on ROCFT copy, immediate, and delayed recall on the same day after recording PSVEP. Results for each element were then summed up to obtain a score for the whole figure, up to 36 points (as there are 18 elements with each element having the maximum score of 2 points.

Results: The Kolmogorov-Smirnov test was used to test the normality and all the data were tabulated as mean ± SD. One-way ANOVA and post hoc Tukey’s test using SPSS 16 revealed that there is a significant difference (P < 0.001) in P100, N75, and N145 latency among the groups. P100 amplitude did not show any significant difference between the groups. ROCFT score on a copy, immediate (after 3 min), and delayed recall (after 30 min) showed significant differences (P < 0.001) among the group. Pearson correlation supported that BMI is positively correlated with latency and negatively correlated with cognition.

Conclusion: High BMI is an important risk factor for delayed nerve conduction and impaired visual executive memory. This test can be used in illiterates to detect mild cognitive impairment. Measurement of inflammatory markers and brain imaging was not done due to the lack of funding, and hence, the exact mechanism behind prolonged latency and diminished cognition among overweight and obese young adults could not be made out.

Key words: Body Mass Index; Electrophysiology; Obesity; Visual Cognition; Visual Evoked Potential