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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 13  |  Issue : 1  |  Page : 43-47

Impact of body mass index on cognitive function among young adults


Physiotherapy Department, SPB Physiotherapy College, Surat, Gujarat, India

Date of Submission01-Oct-2018
Date of Acceptance14-Jan-2019
Date of Web Publication29-Jun-2019

Correspondence Address:
Dr. Salvi Shah
SPB Physiotherapy College, Ugat-Bhesan Road, Surat - 395 005, Gujarat
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/PJIAP.PJIAP_44_18

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  Abstract 

BACKGROUND AND PURPOSE: Cognition is the mental action on the process of acknowledge and understanding through thought, experience, and sense. A glowing body of literature is binding that being overweight (OW) or obese (O) has an effect on cognition as well as on physical functioning. A better understanding of this relationship could help target psychological services and public health strategies more effectively. The aim of the present study was to find out the impact of body mass index (BMI) on cognitive function among young adults.
MATERIALS AND METHODS: A convenient sample of 300 participants aged between 18 and 24 years was selected for the study. Demographic data and anthropometric measurements were taken. After that, BMI was calculated for all participants and participants were divided into two groups: Group A (normal BMI, n = 150) and Group B (OW/O, n = 130). Twenty students were excluded from the study because of their underweight. Rest of the participants (n = 280) were asked to performed Rey Verbal Auditory Learning test (RVALT), Stroop test, and Trail Making test A and B.
STATISTICAL ANALYSIS: Unpaired t-test was used to find out a significant difference in cognitive functions among two groups.
RESULTS: It was found that cognition score (all three tests) obtained by normal BMI group was higher than score obtained by OW/O group (RVALT: P<0.0001, Stroop test: P<0.0001, Trail Making Test: Part A: P < 0.04 and for Part B: P < 0.0001).
CONCLUSION: The present study concluded that high BMI individuals have lower cognitive functions.

Keywords: Body mass index, cognition, young adults


How to cite this article:
Chauhan S, Shah S, Shah S. Impact of body mass index on cognitive function among young adults. Physiother - J Indian Assoc Physiother 2019;13:43-7

How to cite this URL:
Chauhan S, Shah S, Shah S. Impact of body mass index on cognitive function among young adults. Physiother - J Indian Assoc Physiother [serial online] 2019 [cited 2019 Nov 19];13:43-7. Available from: http://www.pjiap.org/text.asp?2019/13/1/43/261820


  Introduction Top


Cognition is the mental action or process of acquiring knowledge and understanding through thought, experience, and senses.[1] It encompasses process such as knowledge, attention, memory and working memory, judgment and evaluation, reasoning and computation, problem solving and decision-making, comprehension, and production of language.[2] Cognitive functions constitute processing, integration, storage and retrieval of information related to memory, attention, association, processing speed, perception, and executive function. Superior cognitive function is key to maintaining a high quality of life as it helps individuals carry out day-to-day activities.[3]

Obesity in youth has received significant attention, as being overweight or obese as a child or adolescent predicts being overweight or obese later in life.[4] Further, childhood and adult obesity have been associated with a number of long-term negative outcomes. Obesity has been determined to be a risk factor for several medical conditions, including hypertension, Type 2 diabetes, heart disease, sleep apnea, and cancer.[5] In addition, increased body mass index (BMI) has been linked to increased risk for the development of both dementia and Alzheimer's disease.[6]

Although the impact of a high BMI on the body of excess is well known and widely studied,[7],[8],[9] and similarly its impacts on health,[10] little is known about the consequences of being overweight or obese on cognitive function.[11] The diverse studies that have linked BMI to cognitive function observe that obesity in old age is associated with lower cognitive scores,[12],[13] but the association between these variables in aging is not yet fully understood. It has also been observed that a high BMI at around 40 years of age precedes a generally lower cognitive ability and cognitive decline in men and women.[14] Being underweight, overweight, or obese has been identified as a risk factor for dementia in old age.[15],[16],[17],[18]

To clarify whether cognition really depends on body mass or fatness in humans, an epidemiological setting comparing the cognitive pattern of participants with different BMI or body fat mass is the better approach. From the literature, conflicting results emerge. Till now, various studies have been done to determine the impact of BMI on cognitive function in children and elderly individuals, and most studies establish a relationship between obesity and cognition as risk factors for developing cognitive impairment; little is known about the impact of BMI on different cognitive functions in young adults.[19] Hence, the present study was undertaken.


  Materials and Methods Top


A convenient sample of 300 participants aged between 18 and 24 years was randomly selected from different colleges of Surat city (interior designing, physiotherapy, engineering, B. Sc., B.com., etc.), after receiving permission from the college. Participants (both males and females) who willing to participate in the study and able to write and read English language were selected for the study. Participants with color blindness, with any known neurological condition, and with any inability to follow test instructions were excluded from the study. All participants were asked to sign the consent form prior to participate in research study. Information about demographic data, educational status, and name of college were obtained from all eligible participants and after that anthropometric measurements such as weight, height, waist circumference, and hip circumference were taken.

Then, BMI was calculated for each participant. From 300 participants, 20 participants were underweight (BMI < 18), so they were not included in the study. The rest of the 280 students were divided into two groups as follows: Group A (normal BMI, n = 150) and Group B (over weight/obese, n = 130).[20]

All of the cognitive tests were performed in classroom. The information about the cognition tests was given to all participants. Participants performed Rey Verbal Auditory Learning test (RVALT), Stroop test, and Trail Making test A and B in randomized order. Reliability and validity of all the tests to measure cognition are good.[21],[22],[23]

RVALT was used to assess episodic memory. An auditory recording of 15 words (e.g., drum, bell, coffee, and school) was played. Immediately after the presentation, participants were asked to write down as many of the words they could remember in any order in 1 min. The list presentation and recall was repeated five times with different lists. After the completion of recording, the author counted and recorded how many words they remembered correctly and how many words they remembered incorrectly. The average between all six trials was calculated for each participant.[24]

Trail Making Test A and B was used to assess perceptual speed. Participants were shown a sample Part A. The author demonstrated the process of connecting the numbers in numerical order from 1 to 8 (sample A). After that, the author demonstrated Part B, which asks the participants to connect the numbers and letters in numerical and alphabetical order (e.g., 1-A-2-B-3-C-4-D etc.). The participants were given sample Part A and sample Part B and then asked to complete it knowing that it is not timed. If any errors were made, the author stopped the participant, addressed the error, and explained why it was wrong. Once they completed sample A and sample B correctly, participants were given Part A and Part B and asked to complete as fast and accurately as possible connecting the numbers. If any mistakes were made here, author stopped the participant and asked them to go back to the last correct circle and continue, while still the timing was noted. The author recorded the time.[24]

Stroop test: A variant of the Stroop test was used to assess executive functioning. First, participants were shown a piece of paper with 44 congruent color words (e.g., “RED” was in red ink) and asked to read as fast as possible. The author recorded the time. Next, the participants were presented with 44 incongruent color words (e.g., “RED” was in blue ink) and asked to read as fast as possible. If there were errors made in either the congruent or incongruent colour words, the author stopped the participant and asked the participant to start from the last correct word. The author recorded the time.[24]

Before performing the tests, the therapist explained each test and demonstrated it in a standardized manner to measure cognition. After performing the tests, the test results were noted by the therapist. All tests are time-based tests so that the time was noted by the therapist with the use of stopwatch. Verbal auditory learning test is the only test which was performed in the group and another two were performed individually in the sequence.

For RVALT score, the number of correct words (average of six trials), for Stroop test score, average of time for reading congruent color word list and incongruent color words list, and for Trail Mailing test score, timing for completing Part A and Part B were noted.

Then, all the data were entered in an Excel sheet. Statistical analysis was done using IBM SPSS 20. A statistical significance level of P < 0.05 was adopted for statistical tests.


  Results Top


A total of 280 participants (169 females and 111 males) were included in the present study. From that, 150 participants were having normal BMI (Group A) and 130 participants were overweight/obese (Group B). The mean age of all participants in Group A was 20.41 years, and for Group B, the mean age was 20.68 years. All the cognitive function tests (RVALT, Stroop test, and Trail Making test [task A and task B]) were performed by all the participants, and the results were noted by the therapist.

Unpaired t-test was used to find out a significant difference in cognitive function between the two groups.

Physical characteristics of all participants in Group A and Group B are shown in [Table 1] and [Table 2] which display the group statistics of age distribution among Group A and Group B. No significant difference was noted for age across the two groups. The mean value of three different cognitive tests for Group A and Group B is shown in [Table 3].
Table 1: Physical characteristics of Group A and Group B

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Table 2: The group statistics of age (years) distribution among Group A and Group B

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Table 3: Mean value of three different cognitive tests for Group A and Group B

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Results of the study showed that there is a significant difference in cognitive function (RVALT, Stroop test, and Trail Making test [Part A and Part B]) between Group A and Group B [Table 3].


  Discussion Top


Results of the present study showed that there was a significant difference between normal BMI and overweight/obese young adult's performance on different measures of cognitive functioning. Our results converge with previous studies, suggesting that overweight/obese individuals demonstrate less efficient cognitive flexibility, a key cognitive control function.[25] Previous studies demonstrated that higher BMI is associated with chronic low-grade inflammation and with augmented production of pro-inflammatory cytokines, which may account for the detrimental effect of dopaminergic-driven cognitive functions observed in obese and overweight individuals.[26],[27] It remains to be investigated whether the cognitive control deficits and associated neuronal dysfunctions [28],[29] observed in individuals with overweight and obesity play a causal role or are instead the consequence of these conditions.[30]

Emerging research proposes a range of plausible mechanisms that might contribute to an independent effect of overweight/obesity on cognitive function including structural brain changes,[31],[32] impaired cerebral metabolism,[33] elevated leptin,[34],[35] and inflammation.[36] Independent associations between obesity and structural brain changes including greater brain atrophy,[31],[32] decreased gray matter volumes,[31],[37] and increased white-matter hyperintensities [38] have been demonstrated. Furthermore, a negative relationship between prefrontal cerebral metabolism and BMI has been identified.[34] Leptin, a hormone contained in body fat, and thus found in greater levels in overweight/obese individuals, has been associated with impaired cognitive performance.[35],[36] While inflammatory proteins (e.g., c-reactive protein), found more commonly in overweight/obese individuals, have also been associated with lower cognitive scores among obese females,[39] inflammatory markers have also been linked with reduced total brain volume,[40] providing further evidence that neuronal degradation might be implicated in the obesity–cognition relationship.

One suggests a direct action of adiposity in neuronal tissue through pro-inflammatory mediators produced by adipocytes and endocrine messengers that respond to food ingestion. Adipose tissue is known as a source of pro-inflammatory cytokines in obese humans and in animal models due to receptor insensitivity to leptin. Most obese people have an altered adipose tissue function caused by the interaction of genetic and environmental factors, which lead to hypertrophy, hypoxia, and a variety of inflammatory processes in the adipose tissue. Visceral fat accumulation may be considered a consequence of a dysfunction of adipose tissue, characterized by changes in cell function, increased lipid storage, and secretion of pro-inflammatory molecules such as cytokines, and inflammatory and procoagulant peptides. One study found that levels of interleukins 1β correlated with adiposity and cognitive impairment. Inflammation, particularly chronic low-grade inflammation, seems to affect several brain functions, from the early development of the brain to the development of neurodegenerative and psychiatric diseases, associated with cognitive deficits and dementia.[41]

In summary, findings of the present study showed that individuals with high BMI may exhibit deficits on different measures of cognitive functioning (e.g., working memory [RVALT], attention, speed, and cognitive flexibility [Stroop test], and visual attention and task switching [Trail mailing test]). This further highlights the urgency to institute public health interventions to promote a healthy weight in young individuals.

One limitation of the study is that it was cross-sectional research. Cross-sectional research only allows for a brief glimpse into the lives of the participants and does not examine how the relationship between physical and behavioral variables affects change over time. Cognitive impairments have been indicated in a number of conditions comorbid with overweight and obesity (such as hypertension and sleep apnea), ones that were not assessed in this study. Diet quality and physical activity may influence cognitive control and weight status and warrant further investigation in relation to the role of cognitive control in overweight and obesity. Important consideration for future research is recent evidence that resistance training can improve cognitive function. Review of the literature suggests that strength training benefits general health as well as cognitive health. Based on the findings in the literature, it may be suggested that researchers in the future account for the aerobic capacity as well as resistance training status of each individual.


  Conclusion Top


The results of the present study concluded that overweight and obese participants have lower cognitive functions as compared to normal BMI individuals. Further research is needed to clarify the mechanism for the same and also for examining the link and directionality between cognition and childhood obesity. Future scope of the study is that the longitudinal study may be performed rather than cross sectional and a uniform method of cognitive function may be utilized for future intervention strategies.

Acknowledgment

Researchers would like to thank all the students, teachers, and principals of the colleges for their kind cooperation and valuable support required for the data collection.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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