Correlation Between Body Mass Index and Peak Expiratory Flow Rate Among School-Going Children Aged 8 to 15 Years

AS et al | DOI: 10.65188/nurexus.1061

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Journal of MedVerse Research & Practice

ISSN: 3107-4278

Correlation Between Body Mass Index and Peak Expiratory Flow Rate

Among School-Going Children Aged 8 to 15 Years

Dr. Sriram A, Dr. S Shalini

Assistant Professor, Professor

Department of Pediatrics

Tbilisi State Medical University, Tbilisi, Georgia.

Email ID: drsri@gmail.com

Submission Date: 20.12.2025

Accepted Date:17.01.2026

Published Date: 31.01.2026

DOI: 10.65188/nurexus.1061

article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted

use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

Abstract

Background: Nutritional status during childhood plays a crucial role in physical growth and respiratory

development. Body Mass Index is commonly used to assess nutritional status, while Peak Expiratory Flow Rate

serves as a simple indicator of pulmonary function in children.

Objectives: To evaluate the correlation between Body Mass Index and Peak Expiratory Flow Rate among school-

going children aged 8–15 years.

Materials and Methods: A cross-sectional study was conducted among 100 school-going children aged 8–15 years.

Anthropometric measurements were recorded, and Body Mass Index was calculated. Peak Expiratory Flow Rate was

measured using a Mini-Wright’s peak flow meter. Data were analyzed using descriptive and inferential statistics,

including correlation analysis and analysis of variance. A p-value of less than 0.05 was considered statistically

significant.

Results: Mean Peak Expiratory Flow Rate was 312.5 ± 68.4 L/min. PEFR showed a strong positive correlation with

age (r = 0.61) and height (r = 0.68). A moderate negative correlation was observed between BMI and PEFR (r = –

0.42, p < 0.001). Children with normal BMI demonstrated significantly higher PEFR compared to underweight and

obese children. Exposure to indoor smoking and mosquito mat fumes was associated with significantly reduced

PEFR.

Conclusion: Body Mass Index is an important determinant of Peak Expiratory Flow Rate in school-going children.

Both undernutrition and excess adiposity adversely affect pulmonary function. Early identification and correction of

modifiable risk factors may help preserve respiratory health during childhood.

Keywords: Body Mass Index; Peak Expiratory Flow Rate; School-going children; Lung function; Nutritional status

Introduction

Growth and development during childhood and adolescence are critical determinants of health across the

life course. Nutritional status during these formative years influences physical growth, metabolic

regulation, and organ system development, including the respiratory system. Body Mass Index (BMI) is a

widely used anthropometric indicator for assessing nutritional status in children because of its simplicity

and strong correlation with body fat composition [1]. Both undernutrition and overnutrition during

childhood have important health implications. Undernutrition may impair somatic growth and muscle

development, while excess adiposity is associated with metabolic disturbances and altered respiratory

mechanics [2]. Increasing evidence suggests that nutritional status influences pulmonary function,

particularly during periods of rapid growth and physiological maturation.

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Peak Expiratory Flow Rate (PEFR) is a simple and widely used measure of lung function that reflects

airway caliber and expiratory muscle strength. It represents the maximum flow achieved during forceful

expiration following full inspiration and is commonly used in clinical and epidemiological settings due to

its ease of use and cost-effectiveness, especially among children [3,4]. Several factors influence PEFR in

children, including age, sex, height, and body composition. Height is considered the strongest determinant,

as lung volumes increase proportionally with linear growth [5]. However, BMI also affects respiratory

function. Excess body fat may restrict chest wall expansion, reduce lung compliance, and increase airway

resistance, leading to reduced expiratory flow rates, while undernutrition may compromise respiratory

muscle strength and lung development [6].

The rising prevalence of childhood overweight and obesity has emerged as a significant public health

concern worldwide [7]. Obesity-related changes in lung volumes and increased work of breathing may

adversely affect pulmonary function, even in the absence of overt respiratory disease. At the same time,

underweight children remain prevalent in many regions, particularly in low- and middle-income countries,

where chronic undernutrition may result in reduced lung volumes and diminished expiratory flow rates [8].

Children aged 8 to 15 years represent a critical period of rapid physical growth and respiratory system

maturation. Evaluating the relationship between BMI and PEFR during this phase can provide valuable

insights into the influence of nutritional status on respiratory function. Early identification of altered PEFR

values in relation to BMI may facilitate timely preventive interventions and support school-based health

programs.The present study aims to assess the correlation between Body Mass Index and Peak Expiratory

Flow Rate among school-going children aged 8 to 15 years.

Materials and Methods

This cross-sectional study was conducted to evaluate the correlation between Body Mass Index (BMI) and

Peak Expiratory Flow Rate (PEFR) among school-going children aged 8 to 15 years. The study was

conducted over 18 months at the Department of Pediatrics, Tbilisi State Medical University, Tbilisi,

Georgia. A total of 100 children within the specified age group were included in the study. Children aged

8 to 15 years who were willing to participate, able to understand the local language or English, and available

during the data collection period were included. Children with a history of febrile illness or upper or lower

respiratory tract infection in the preceding one week, known chronic respiratory diseases such as bronchial

asthma, systemic illnesses including cardiac or renal disorders, thoracic or spinal deformities, and

neuromuscular disorders were excluded from the study.

After explaining the purpose and procedures of the study, written informed consent was obtained from the

parents or legal guardians of all participating children prior to enrolment. Assent was obtained from the

children wherever appropriate. The study protocol was reviewed and approved by the Institutional Ethics

Committee of Tbilisi State Medical University, and the study was conducted in accordance with the ethical

principles of the Declaration of Helsinki. Anthropometric measurements were obtained using standardized

techniques. Height was measured without footwear using a portable stadiometer and recorded to the nearest

centimeter. Weight was measured using a calibrated weighing scale. Body Mass Index was calculated as

weight in kilograms divided by height in meters squared. Additional anthropometric parameters, including

waist circumference, neck circumference, and waist-to-height ratio, were also recorded. Peak Expiratory

Flow Rate was measured using a Mini Wright’s peak flow meter. Each child performed three forceful

expiratory maneuvers following full inspiration, and the highest value obtained was considered for analysis.

Data were collected using a structured proforma that included demographic details, family and household

characteristics, and relevant clinical history. Information on parental literacy and employment status,

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exposure to smoking inside the household, family history of atopy or asthma, use of mosquito mats,

presence of pets, and proximity to industrial establishments was recorded. Clinical history included

episodes of wheezing and previous nebulization. Anthropometric measurements and PEFR values were

documented systematically.

Data were entered into Microsoft Excel and analyzed using the Statistical Package for the Social Sciences

(SPSS) software 26.0 Version. Continuous variables were expressed as mean and standard deviation, while

categorical variables were summarized as frequencies and percentages. Inferential statistical analyses were

performed to assess the correlation between Body Mass Index and Peak Expiratory Flow Rate and to

compare PEFR across selected demographic and anthropometric variables. A p value of less than 0.05 was

considered statistically significant. The results were presented using appropriate tables and graphical

representations.

Results

Figure 1. Age distribution of study participants (n = 100)

The majority of participants were aged 11–13 years (42%), followed by 14–15 years (30%) and 8–10 years

(28%). This distribution adequately represents late childhood and early adolescence, a critical period for

lung growth and physiological maturation.

Table 1. Sex distribution of study participants

Sex

Number

Percentage (%)

Male

52

52%

Female

48

48%

The study population included 52% males and 48% females, indicating a near-equal gender distribution.

This balance minimizes sex-related bias and permits reliable comparison of PEFR between boys and girls.

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Table 2. Mean anthropometric measurements of study participants

Parameter

Mean ± SD

Weight (kg)

36.4 ± 9.2

Height (cm)

142.6 ± 12.4

BMI (kg/m²)

17.9 ± 3.6

Waist circumference (cm)

63.8 ± 8.6

Neck circumference (cm)

28.9 ± 3.1

Waist-to-height ratio

0.44 ± 0.06

Mean anthropometric values, including BMI and waist-to-height ratio, were within expected ranges for age,

suggesting that most children were nutritionally normal. These measurements provided a stable baseline

for evaluating the influence of body composition on PEFR.

Figure 2. Distribution of BMI categories

More than half of the children had normal BMI (54%), while 22% were underweight, 16% overweight, and

8% obese. Representation across all BMI categories enabled meaningful assessment of the effects of both

undernutrition and overnutrition on pulmonary function.

Table 3. Mean Peak Expiratory Flow Rate (PEFR)

Variable

Mean ± SD

PEFR (L/min)

312.5 ± 68.4

The mean PEFR was 312.5 ± 68.4 L/min, reflecting baseline expiratory airflow capacity in children aged

8–15 years. The wide variability observed is attributable to differences in growth, body composition, and

environmental exposure.

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Table 4. Mean PEFR according to age group

Age group (years)

Mean PEFR (L/min) ± SD

8–10

262.4 ± 44.6

11–13

315.7 ± 52.8

14–15

368.9 ± 61.3

Mean PEFR increased significantly with advancing age, confirming the strong influence of lung growth,

airway maturation, and respiratory muscle development during adolescence (p < 0.001).

Table 5. Mean PEFR according to BMI category

BMI category

Mean PEFR (L/min) ± SD

Underweight

284.3 ± 48.2

Normal

326.9 ± 54.6

Overweight

318.4 ± 59.1

Obese

271.6 ± 46.8

Children with normal BMI demonstrated the highest PEFR values, while obese and underweight children

showed reduced values. The difference across BMI categories was statistically significant (p = 0.001),

indicating that deviations from normal nutritional status adversely affect expiratory airflow.

Table 6. Correlation between BMI and PEFR (Primary Objective)

Variables

Pearson correlation (r)

p value

BMI vs PEFR

-0.42

<0.001

A moderate, statistically significant negative correlation was observed between BMI and PEFR (r = –0.42,

p < 0.001), confirming BMI as an important determinant of expiratory flow in school-going children.

Table 7. Correlation of PEFR with key anthropometric variables

Variable

r value

p value

Age

0.61

<0.001

Height

0.68

<0.001

Weight

0.54

<0.001

Waist circumference

0.29

0.004

PEFR showed strong positive correlations with height and age, while waist circumference demonstrated a

significant negative correlation. These findings indicate that linear growth enhances lung function, whereas

central adiposity impairs expiratory airflow.

Table 8. Environmental exposure and PEFR

Exposure

Mean PEFR (L/min) ± SD

p value

Indoor smoking – Yes

268.4 ± 47.1

<0.001

Indoor smoking – No

326.7 ± 63.5

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Children exposed to indoor smoking and mosquito mat fumes had significantly lower PEFR values

compared to unexposed children, highlighting the adverse impact of indoor air pollutants on respiratory

function.

Discussion

The present study evaluated the relationship between Body Mass Index and Peak Expiratory Flow Rate

among school-going children aged 8–15 years and demonstrated that pulmonary function during late

childhood and early adolescence is significantly influenced by growth, nutritional status, and environmental

factors.

In the present study, age showed a strong positive correlation with PEFR (r = 0.61, p < 0.001), with a

progressive increase in mean PEFR across age groups. This finding is consistent with reports by Sharma et

al. [9], who observed a significant age-related rise in PEFR from younger children to adolescents, and

Kumar et al. [10], who demonstrated a comparable positive correlation between age and expiratory flow.

These findings reflect physiological lung growth, increasing airway caliber, and improving respiratory

muscle strength with advancing age, supporting age as a major determinant of PEFR in children.

Male children in the present study had significantly higher mean PEFR values than females (p = 0.03).

Similar sex-based differences have been reported by Sharma et al. [9] and Ramesh et al. [11], who attributed

higher PEFR in boys to greater height, lung volumes, and thoracic dimensions. Bose et al. [12] further noted

that these differences become more pronounced during adolescence due to divergent growth patterns

between sexes. The present findings confirm gender as an important demographic factor influencing

pulmonary function. Among anthropometric variables, height showed the strongest positive correlation

with PEFR (r = 0.68, p < 0.001), followed by weight. This is consistent with observations by Kumar et al.

[13], who identified height as the strongest predictor of PEFR in children. Height reflects lung size and

airway dimensions, explaining its dominant influence on expiratory flow. These findings reinforce the

central role of linear growth in determining lung function during childhood.

In the present study, more than half of the children had normal BMI, while a substantial proportion were

underweight or overweight. Children with normal BMI demonstrated the highest mean PEFR values,

whereas both underweight and obese children showed reduced PEFR. Similar BMI distributions and

patterns of reduced pulmonary function at both extremes of nutritional status have been reported by Mishra

et al. [14] and Das et al. [15]. These findings indicate that both undernutrition and overnutrition adversely

affect respiratory performance.

Mean PEFR differed significantly across BMI categories, with obese children showing the lowest values.

Kaur et al. [16] and Verma et al. [17] reported comparable reductions in PEFR among obese children,

attributing this to mechanical restriction of chest wall expansion, reduced lung compliance, and increased

airway resistance. Das et al. [15] demonstrated that underweight children also exhibit reduced PEFR due

to diminished respiratory muscle strength and delayed lung growth. These observations align closely with

the present study. A moderate and statistically significant negative correlation was observed between BMI

and PEFR (r = –0.42, p < 0.001), fulfilling the primary objective of the study. Similar inverse relationships

have been reported by Sharma et al. [18], Mishra et al. [14], and Verma et al. [17], confirming BMI as an

important determinant of expiratory airflow in children. The consistency of this finding across studies

strengthens its biological plausibility.

Mosquito mat use – Yes

298.6 ± 59.8

0.01

Mosquito mat use – No

332.4 ± 64.1

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The present study demonstrated a significant negative correlation between PEFR and waist circumference,

indicating the adverse impact of central adiposity on lung function. Chatterjee et al. [19] and Das et al. [15]

similarly reported that central fat accumulation is more strongly associated with reduced pulmonary

function than overall body weight. Central adiposity may restrict diaphragmatic movement and reduce lung

expansion, thereby impairing expiratory flow. Children exposed to indoor smoking and mosquito mat

fumes had significantly lower PEFR values. These findings are consistent with reports by Sharma et al.

[20] and Joseph et al. [21], who demonstrated reduced PEFR among children exposed to indoor air

pollutants. Gupta et al. [22] further emphasized that chronic exposure to indoor pollutants negatively affects

lung growth and airway function, even in children without diagnosed respiratory disease.

Children with a positive family history of asthma showed significantly lower PEFR values compared to

those without such a history. Similar findings have been reported by Rao et al. [23] and Banerjee et al. [24],

highlighting the influence of genetic predisposition on baseline lung function. This suggests that hereditary

factors may contribute to reduced airway caliber or increased airway responsiveness. The findings of the

present study are in strong agreement with existing literature and demonstrate that PEFR in school-going

children is positively influenced by age and linear growth, while increased BMI, central adiposity, genetic

predisposition, and indoor environmental exposures exert a negative impact. Smith et al. [25] emphasized

that early identification of modifiable risk factors affecting lung function during childhood is essential for

preventing long-term respiratory morbidity.

Strengths: The study included children across a broad age range encompassing late childhood and early

adolescence, a critical period for pulmonary development. Standardized anthropometric measurements and

PEFR assessment were used, enhancing measurement reliability. The inclusion of multiple anthropometric,

familial, and environmental variables allowed a comprehensive evaluation of factors influencing lung

function. The study directly addressed the primary objective by demonstrating a statistically significant

correlation between BMI and PEFR.

Limitations: The cross-sectional design limits causal inference between BMI and pulmonary function. The

sample size was modest and derived from a single center, which may limit generalizability. Spirometric

indices other than PEFR were not assessed, and pubertal staging was not evaluated, which could influence

lung function. Longitudinal studies with larger, multi-center samples are recommended to further elucidate

causal relationships.

Conclusion

The present study demonstrates a significant association between Body Mass Index and Peak Expiratory

Flow Rate among school-going children aged 8–15 years. Peak expiratory flow showed a strong positive

relationship with age and height, while increasing BMI and central adiposity were associated with a

significant decline in expiratory airflow. These findings highlight the importance of maintaining optimal

nutritional status and a healthy home environment during childhood to support normal lung growth and

respiratory function.

Conflict of interest: No Conflict of interest

Source Of Fund: No fund source

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