Childhood obesity is the current public health concern in low and middle-income countries, and warrants measures to intervene early. World Obesity atlas published in 2019 presented projections that childhood obesity may affect more than 150 million adolescents between the ages 10-19 worldwide by 2030. This contributes to about 12.91% of all children and adolescents globally. Though South East Asia, has relatively low childhood obesity levels it has been postulated to have more than 25 million adolescents aged 10-19 affected by obesity by 2030. India is predicted to have over 27 million children with obesity, which amounts to 1 in 10 of all children globally.[1] Increased occurrence of obesity amidst school children is becoming an upsetting public health issue. According to the National Family Health Survey (NFHS) conducted in India, a rapid surge in overweight and obesity of 125 per cent (from 2.4 per cent to 5.4 per cent) and 288 per cent (from 1.7 per cent to 6.6 per cent) respectively has been observed among adolescent girls and boys between NFHS 3 (2005-06) and NFHS 5 (2019-21).[2] Peak expiratory flow rate (PEFR)measurement is a simple measure of the maximal flow rate that can be achieved during forceful expiration following full inspiration. It is measured in litres per minute(L/min). PEFR of any child is dependent on variables such as age, sex, height, weight etc. It depends on the voluntary effort and muscular strength of the child.[3] A mini-Wright's peak flow meter (mWPFM), which is simple to use and can be used to monitor peak expiratory flow rate. It has been shown that there is a wide variation in the lung function parameters with different regions within the same country.[4] PEFR also directly indicates the child's nutritional health apart from its role in assessment of lung function. Nutritional standards are a major determinant of ventilatory capacity in children. With increasing age, height and lung capacities increase within the same age group. A well nourished child with greater height will have a greater muscular effort that can give a higher PEFR reading.[5] Children who are obese have reduction in alveolar surface area relative to the volume of the lung.[5,6] They not only have external mechanical compression on the thorax and lung but also changes within the lung.[7] It has been shown that there is a significant correlation between BMI and PEFR in study done on young adults. There are several factors that have an impact on the PEFR and they include the expiratory muscle strength, airway competency and recoil of the lungs.[8] Obesity is considered a disease modifier of respiratory disorders like asthma and Obstructive sleep apnoea syndrome (OSAS).[9] Studies have shown that prevalence of asthma is more in obese children and they are more symptomatic and need emergency department services frequently. It has been found that the presence of obesity results in poor response to treatment measures for asthma and OSAS.[10] Reversibility of airflow obstruction in asthma can be identified by using a peak flow meter. The device is useful in diagnosis and management of asthma. Regular monitoring of PEFR values in asthma help to identify triggers and monitor response to therapy. PEFR has helped to reduce the frequency and severity of exacerbations of asthma and improve quality of life.[11] Aims and Objectives To establish the relationship between the Peak Expiratory Flow Rate and Body Mass Index among obese and non-obese adolescents and to find out the correlation between age and gender and PEFR in obese and non-obese adolescents.

This was a case control study done on adolescents between 14-17 years studying in high school and higher secondary Government schools in Chennai,Tamil nadu during the period December 2022- June 2024. Sample size calculation. Based on the study done by Zuhal Gundogdu et al.,[12] sample size was calculated with mean difference of 30 L/min ,95% CI ,80% power to be 196. So, a total of 200 students were included in the study. Obese adolescents of age 14-17years studying in high / higher secondary Government schools were considered as cases while non obese adolescents in the same age group studying in the same school were considered as controls. Adolescents with history of acute respiratory tract illness in the past one week, nocturnal cough, oro- facial surgery, chronic respiratory illness, structural anomalies of chest wall and spine and asthma were excluded from the study. METHODOLOGY The schools were selected by systematic random sampling from the five Corporation zones in Chennai which were adjacent to the study centre. One school was selected randomly from each zone and 20 cases and 20 controls from each school were recruited. The study was commenced after obtaining approval from the Institutional Ethics Committee and permission from Chennai Corporation chief Education Officer and school Headmaster/headmistress. After being gathered in one location, students were given information about the study and given consent forms for parental consent. Only those students who returned with signed parental consent forms were included in the study which was performed the next day. Age was calculated from the date of birth in whole years. Weight was measured with a precision of 0.1 kg using a digital scale. To measure weight, bulky garments and shoes were removed. The surface of the scale was lightly touched to switch on the display till it displayed "0." The students were directed to stand on the scale by placing their feet in the middle of the platform, slightly apart and weight was measured. Height was measured using a stadiometer after removing shoes, cap and hair bands. The heads, buttocks, back of heels of study participants were in touch with the vertical rod. The head was positioned appropriately using the Frankfurts plane. The movable headboard was brought down until it made firm contact with the top of the head. The measurement that was closest by 0.5cm was noted. After measuring the height and weight, Body Mass Index (BMI) was calculated and interpreted using the Indian Academy of Pediatrics (IAP) growth charts. PEFR was performed using a mini-Wrights peak flow meter. The pointer was moved to 0 and mouthpiece was fixed to the flow meter. The student was asked to take a deep breath followed by placing the peak flow meter in the mouth with tight seal around it, the student was asked to blow as hard and fast as possible. The position of the indicator was noted. Each student was asked to do the procedure thrice and the highest of the three recordings was considered. Operational Definitions: Body mass index (BMI) was calculated as the ratio of weight(kg) to the square of height(m2) and interpreted as per IAP growth chart 2016 according to the age-specific cut-off. Over weight: If BMI is more than 23 adult equivalent (According to IAP chart). Obesity: If BMI is more than 27 adult equivalent. (According to IAP chart) Statistical analysis BM SPSS Statistics for Windows, Version 29.0, was used to analyze the data after it was entered into Microsoft Excel 2016 (IBM Corp., Armonk, NY). For categorical variables, descriptive statistics such as frequency analysis and percentage analysis were employed to characterize the data, whereas for continuous variables, the mean and standard deviation were used. The Independent sample t-test was used to determine whether there was a significant difference between the bivariate samples in the independent groups. The probability value of <0.05 was regarded as a significant level.

This study was done on 200 school students of which there were 100(50%) obese adolescents(cases) and 100(50%) non-obese adolescents(controls). They were between the ages of 14 and 17 years. The number of students in each age category ranged from 47 (23.5%)to 53(26.5%). The boys and girls were equally distributed (100 boys and 100 girls). (Table 1) Table 1: Age and Gender distribution among the study population Age Frequency Percent 14 years 51 25.5 15 years 49 24.5 16 years 53 26.5 17 years 47 23.5 Total 200 100.0 Gender Male 100 50.0 Female 100 50.0 Total 200 100.0 The mean (SD) PEFR among the obese students was 251.90(16.74) and among the non obese students it was 329.90(22.18). Comparison of the mean (SD) PEFR values revealed a significantly lower value among obese students (p<0.0005). (Table 2) Table 2: Comparison of PEFR between obese and non-obese students by Independent sample t-test Variable Groups N Mean SD t-value p-value PEFR Non-Obese 100 329.90 22.18 28.071 0.0005 ** Obese 100 251.90 16.74 ** highly significant p < 0.01 The mean (SD) PEFR among the obese boys [263.8(22.3)] was significantly lower when compared to the non- obese boys [348.4(30.80]. (p<0.0005). The mean (SD) PEFR among the obese girls [240.0(13.1)] was significantly lower when compared to the non- obese girls[311.4(29.4] (p<0.0005). The mean (SD) PEFR values were higher in the boys as compared to the girls. (Table 3) Table 3: Comparison of gender among the obese and non-obese students using Independent sample t test Variable Gender N Mean SD t-value p-value PEFR Male Non-obese 50 348.4 30.8 40.201 0.0005 ** Obese 50 263.8 22.3 Female Non-obese 50 311.4 29.4 26.946 0.0005** Obese 50 240.0 13.1 ** highly significant p < 0.01 Table 4: Comparison of age among the obese and non-obese students using Independent sample t test Variable Age N Mean SD t-value p-value PEFR 14 years Non-obese 26 331.5 21.3 14.985 0.0005 ** obese 25 252.8 15.7 15 years Non-Obese 24 330.8 22.6 13.726 0.0005 ** Obese 25 252.0 17.3 16 years Non-Obese 30 329.3 22.3 13.390 0.0005 ** Obese 23 253.5 17.7 17 years Non-Obese 20 327.5 24.0 12.381 0.0005 ** Obese 27 249.6 17.0 ** highly significant p < 0.01 The mean (SD) PEFR among the obese students 14 years of age was 252.8(15.7) and among the non-obese students in the same age category was 331.5(21.3). Among students who were 15 years of age the mean (SD) values of PEFR were 252.0(17.3) in obese and 330.8(22.6) in non-obese group. Obese students who were 16 years of age had a mean (SD) PEFR of 253.5(17.7) while the value for non-obese students was 329.3(22.3). 17year old obese students had recorded a mean (SD) PEFR of 249.6(17.0) as against 327.5(24.0) among the non-obese students. Comparison of the mean (SD) PEFR values revealed a significantly lower value among obese students (p<0.0005). (Table 4)

This study was done to compare peak expiratory flow rate in obese and non-obese adolescents between the ages of 14 and 17 years studying in urban schools. We found that obese adolescents had significantly lower mean PEFR when compared to non-obese adolescents. Obese boys had a significantly lower mean PEFR when compared to non -obese boys. Similar trend was observed in girls. The mean PEFR in girls was lower than that of boys. We also found that lower mean PEFR values in obese adolescents as compared to non -obese adolescents in all the four age groups studied (14 years,15 years,16 years and 17 years). Several studies done across the world have shown varied association between body mass index and PEFR. Our study observed that PEFR was found to be low in those with a high BMI and obese adolescents had a lower mean PEFR compared to non-obese adolescents. Similar observations were made by previous studies.[12,13,14,15] Nepal A in a study done in Kathmandu found that both BMI and height had a positive correlation with PEFR. Mean peak expiratory flow rate was observed to increase with increase in body mass index and was found to decrease when the BMI approached overweight range.[16] Jana SK observed a statistically significant mean difference in PEFR between normal (498/L) overweight (488/L), and obese (391/L) males and similar difference in female normal, overweight, and obese individuals (377 L/min, 348 L/min, and 325 L/min, respectively) wherein obese individuals had lower PEFR than normal individuals.[14] Lower levels of PEFR are due to reduction in lung volume and capacity in obese individuals as compared to healthy individuals. Lung function studies have shown reduction in total lung capacity, forced vital capacity and also reduction of the forced expiratory volume after one second. It was supportive of a restrictive respiratory pattern associated with obesity.[17] Obesity can cause decrease in the lung compliance and thoracic cavity. It was shown that obesity can lead to respiratory muscle dysfunction and increased airway resistance due to excess deposition of fat.[18] Correlations between obesity and pulmonary function have been studied extensively. One leading hypothesis postulate that increased adiposity in the thoracoabdominal region limits the movement of the musculature of the region and thus may impair appropriate lung mobility and hence decrease ventilation. Furthermore, adipose tissue, due to its paracrine and endocrine functions, secretes cytokines and other bioactive mediators that are pro-inflammatory.[19] Contrary findings were noted by Babu RV who studied the association of PEFR with overweight. He observed that PEFR of obese group was higher than that of non-obese and overweight groups. Individuals who obese were found to have higher PEFRs than those who were normal.[20] Study by Gupta M observed that there was an increase in mean PEFR with increase in BMI supporting a positive correlation similar to that of height and weight.[5] Our study found that the mean PEFR was significantly lower in girls as compared to boys. Boys had a higher PEFR than girls because they had more muscle mass than girls did. Similar observations were made in other studies.[5,14,21] Parikh S observed that boys showed higher mean PEFR value (282.53 L/min) compared to girls(270/.79 L/min).[22] Abraham B noted that the mean PEFR among boys was 201.13 ± 44.39 L/min, while the same for girls was 194.01 ± 47.94 L/min. [23]Study by Jana SK revealed a negative correlation between BMI and PEFR for both males (r = -0.512) and females (r = -0.539).[14] Gupta M in her study done in school children in Mumbai noted that the mean PEFR increased as BMI increased in girls and boys. For any given BMI mean PEFR value in boys was higher than those of girls. The variation in PEFR with gender was said to be due to the difference in growth of airway and the expiratory muscle effort. Other factors like nutrition, genetic factor and the environment may play a role in causing a variation of PEFR values.[5] In the present study we did not observe an increase in mean PEFR values with age as our study population included narrow age ranges. However, Parikh S observed that the PEFR values increased with age in both boys and girls probably because their study population included children and adolescents[22] while our study group was restricted to adolescents. Study by Vijaykrishna et al. observed that PEFR increased with age and there was a positive correlation between age and PEFR. This was attributed to musculoskeletal growth, nutrition and body surface area which showed an increase with age.[24] Similar observations were made by Mittal who also noted a significant positive correlation of PEFR with age in their study done among school children in Punjab, India.[25] Similar observations were made by Thangavel A et al.[26] and Gunasekaran A [27] in their studies. LIMITATIONS This study was carried out in Government schools which may cater to children of the middle and lower income groups only. Children from higher socio economic status may not be included. As the schools were selected from the zones adjacent to the study centre, it may not reflect the situation from other zones.

The present study observed that obese adolescents had significantly lower mean PEFR when compared to non-obese adolescents. This observation was uniform throughout the various age groups studied. Similar observation was seen in obese boys and girls when compared to their non-obese counterparts. The mean PEFR values were lower in girls compared to boys. The association between BMI and PEFR indicates that being obese is a significant risk factor that may alter lung function in the pediatric population. Adoption of healthy eating habits with regular exercise will help to prevent future complications of obesity especially respiratory morbidity. Steps must be taken in early childhood to avoid obesity in teenage and adulthood.

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