Effect of age, gender, and body mass index on peak expiratory flow rate and other pulmonary function tests in healthy individuals in the age group 18-60 years

Abstract

Background: Normal ageing and increasing body mass index (BMI) are related to decline in lung functions in adults in both genders. Females are more likely than age and height-matched males to show smaller lung size and diffusion surface, lower maximal expiratory flow rate, and reduced airway diameter. Lung mechanics and respiratory muscle strength, thoracic compliance, airway resistance, and elastic recoil of the lungs determine the pulmonary function tests (PFTs), and these tests are known to differ with age, sex, socio-economic status, cultural factors, and geographical region of the subject and are related to weight, height and BMI of the individuals. Aim and Objectives: The present study is planned to assess the peak expiratory flow rate (PEFR) and other PFTs and to evaluate the effect of age, gender and BMI on these lung functions. Materials and Methods: This study consists of 200 healthy individuals of age group 18–60 years. A sample was stratified into 5 age groups, and on the basis of BMI, the subjects were categorized as underweight, normal, overweight, and obese. Anthropometric measurements were recorded using standard procedures. PEFR was recorded using Wright’s peak-flow meter and forced vital capacity (FVC), Forced Expiratory Volume in 1 s (FEV1), FEV1/FVC, FEF25–75%, FEF2–1.2, slow vital capacity (SVC), and maximum voluntary ventilation (MVV) were analyzed using Expirograph (Helios 401, RMS, India). Chi-square test was used for analysis of categorical variables. For comparison of two groups, unpaired t-test was used and to assess the relation between the variables, Pearson’s co-relation was used. One way ANOVA was used to compare the difference between the means of more than two groups and Tukey post hoc analysis was done for multiple comparisons. Results: There was highly significant difference in the mean values of PEFR and other PFTs (P < 0.000) among the 5 age groups and a significant difference between younger and older age groups. PEFR, FVC, FEV1, FEV1/FVC, FEF25–75%, FEF0.2–1.2, SVC, and MVV were negatively correlated with age (r = −0.514, −0.535, −0.568, −0.255, −0.566, −0.516, −0.304, −0.523, respectively). Females showed reduced mean values of PEFR, FVC, FEV1, FEF25–75%, FEF0.2–1.2, SVC, MVV when compared to males (P < 0.000), and the differences in the mean values were significantly high. Highly significant difference was seen in the mean values of PEFR and other PFTs among the categories of BMI (P < 0.000). The mean values of FVC, FEV1, FEV1/FVC, FEF25–75%, FEF0.2–1.2, MVV were lower among underweight compared to their mean values among individuals with normal BMI. There was negative correlation between PEFR, FVC, FEV1, FEF25–75%, FEF0.2–1.2, SVC, MVV, and BMI (r = −0.327, −0.254, −0.238, −0.269, −0.254, −0.236, −0.195, respectively). Conclusions: PFTs aid in the prompt and accurate diagnosis of respiratory disorders, such as asthma, chronic obstructive pulmonary disease allowing for efficient management by encompassing a thorough understanding of the disease and exercise respiratory training regimens even in otherwise healthy individuals. The present study showed that PEFR and other PFTs decrease with advancing age and BMI and females showed reduced lung functions compared to males.