Research Journal of Recent Sciences _________________________________________________ ISSN 2277-2502 Vol. 2(2), 28-32, February (2013) Res. J. Recent Sci. International Science Congress Association 28 Correlation between Body Mass Index and Peak Expiratory Flow Rate of an Indigenous Nigerian Population in the Niger Delta Region Joffa Paul Kwaku Price Nwafor Arthur2 and Adienbo Ologhaguo MacstephenDept. of Physiology, Faculty of Basic Medical Sciences, College of Health Sciences, Niger Delta University, Wilberforce Island, NIGERIA Dept. of Human Physiology, Faculty of Basic Medical Sciences, College of Health Sciences, Port Harcourt, NIGERIA Available online at: www.isca.in Received 15th September 2012, revised 20th October 2012, accepted 6th December 2012Abstract This study establishes the relationship between peak expiratory flow rate (PEFR) and body mass index (BMI), in a representative sample of 1133 subjects in oil and gas exploitation and exploration environments in Epebu and Okodi in Izon communities, Bayelsa State, Nigeria, comprising 601(or 53%) males and 532(or 47%) females of comparable equal age. The mean PEFR value for the cohort was 367.47±106.67L/min while that for males were higher than that for females, and suggests that continuous and prolonged exposure to oil and gas production environment leads to diminution in peak expiratory flow rate. BMI for women fell within the spectrum of the normal adult body mass index cut off point, somewhere in between 20 - 22 kg/m2 which represents the relatively small body frame of female adults. While BMI for males was suggestive that men are likely predisposed to developing overweight; their body mass fell within the pre-obese spectrum of 25 – 27 kg/m. Our study indicates that weight gain in males might probably be attributed to the influence of genetic factors and environment on eating behaviour as well as sedentary activity; and that the inhibants of Izon communities in the Niger Delta region of Nigeria may have respiratory and pulmonary disorders related to prolonged exposure to potentially dangerous chemicals from oil and gas flared in the environment. Key words: BMI, peak expiratory flow rate, Nigeria, Niger Delta. Introduction Over the last four decades, environmental associated harmful toxic air pollution through venting and flaring wasteful “solution gas”, global warming, climate change and extremes of temperatures had been a great concern in the Niger Delta Region of Nigeria, more specifically, Bayelsa State. Bayelsa state is the major oil and gas producing area and potentially dangerous chemicals1,2 are being introduced into the environment all the time without desirable monitoring of the emission. More so, the effect of respirable suspended particulate matters and other noxious environmental hazards such as nitrogen dioxide, sulphur dioxide, and carbon monoxide on respiratory performance is also poorly understood. The available data on the suspended particulate matters in air of the Niger Delta region as well as in other cities of Nigeria is scanty. Whether these changes are reflected in lung function and body mass changes of individuals was the subject of this study in the population of Nigerians in the Niger Delta region. The primary aim of this study therefore was to establish the relationship between peak expiratory flow rate (PEFR)- the caliber of the airways which serves as valuable tool for diagnosis and treatment of lung functions and body mass index (BMI) - a powerful tool for categorizing individuals weight and height in health and in disease for an indigenous Izon community in the Niger Delta region of Nigeria whose lifestyle and socio-economic factors might have been influenced through oil and gas exploration and exploitation which is of clinical significance. Material and MethodsSubjects and Study Area: Peak expiratory flow rate (PEFR) and body mass index (BMI) for apparently healthy indigenous populations in Izon rural communities in oil exploitation and exploration environments -Epebu and Okodi in Bayelsa State, Nigeria comprising 1133 subjects 601(or 53%) males and 532(or 47%) females who had lived in the communities for more than half their lives were investigated. Epebu and Okodi districts are riverine villages in Ayama development area of Ogbia local Government area, about one and half hour drive by speed boat from the state capital, Yenagoa, Bayelsa state. Selection of Subjects: The following criteria were required for acceptance as a 'normal' subject- No history of cardiopulmonary disease, capacity to co-operate adequately during the test, and no evidence or history of disease which might affect pulmonary function. Consent was sort voluntarily from each prospective participant by way of a request-for-consent/ questionnaire form, explaining the nature of the investigation to enable the participant to decide whether or not to participate in the study. Peak Exploratory Flow Rate Procedure: The peak expiratory flow rate was determined as previously described4,5. Using Wright’s peak flow meter. The subjects were asked to stand in Research Journal of Recent Sciences ______________________________________________________________ ISSN 2277-2502Vol. 2(2), 28-32, February (2013) Res. J. Recent Sci. International Science Congress Association 29 an upright position with the peak flow meter held horizontally in front of their mouth and allowed to take a deep breath in, and closed the lips firmly around the mouthpiece, making sure that no air leaks around the lips. The subject was asked to breathe out as hard and as fast as possible and the around the lips. The subject was asked to breathe out as hard and as fast as possible and the number indicated by the cursor was noted and the sequence was repeated twice more, thus obtaining three readings. The highest or best reading of all three measurements was taken as the peak flow rate. Body Mass Index (BMI) Determination: The participants’ height and weight were measured using standard clinic scales, their body mass index (BMI) was calculated from the relationship- body weight in Kilograms/ height in meters squared, where underweight was 18.5 kg/m, normal 18.5–24.9 kg/m, overweight 25.0–29.9 kg/m and obese 30.0 kg/m2 6. Data Analysis: Statistical analysis was done using SPSS version 17.0 and Microsoft office excel 2007.Values were analyzed based on age, sex, BMI, and PEFR. The Z test was used to compare the mean for male and female at P 0.05. The ANOVA was used to compare the various mean for the BMI group at P 0.05. Results and DiscussionThe mean age, PEFR and BMI values measured in a representative sample of 1133 subjects in oil exploitation and exploration environment in Bayelsa State, Nigeria, are presented in table-1. The mean PEFR value for the cohort was 367.47±106.67L/min while that for males were significantly higher (p0.05) than that for females, table-1. Also, the percent mean difference was 7.74%. BMI values for males, shown in table-1 were higher than that for females making an overall mean difference in BMI of 2.79± 1.67 kg/m; The males tend to be overweight while the females have a normal BMI values, as shown in table-1. Pearson correlation shows a significant negative correlation between age and PEFR for the overall population (r= -0.347, p0.01; figure 1) for males (r= -0.405, p0.1) and for females(r= -0.384, p0.01). Table 2 shows that PEFR values significantly declined with increasing age. Those in the age group 20 to 29 years had the highest values of PEFR while those in the age range .71;㈀60years the lowest values. Further, tables-3 shows that there were statistically significant variations in PEFR and BMI. From table-3, obese subjects, which represented 14% of the overall population, had higher PEFR values (374±11498 L/min) while those 18.5kg/m had the lowest PEFR values (296±73.12 L/min which represented 3.5% of the population; While of the normal subjects (48%), with BMI 18.5 – 24.9kg/m, had normal PEFR values. Correlation study shows positive relationship between PEFR and BMI for the overall population (r = 0.096, p 0.01, figure 2), for males (r = 0.158, p 0.01) and for females (r = 0.065, p 0.01). The complex interplay in relation to changes in body mass index (BMI) and peak expiratory flow rate (PEFR) of individuals in the Niger Delta region in particular, Bayelsa State, Nigeria, as a result of the consequences of oil and gas production is poorly understood. PEFR measurements - the caliber of the airways are valuable tools in lung functions studies for diagnosis and treatment, and in epidemiological and occupational studies for identifying the presence of airflow limitation, assessing its severity and variation; While BMI assessment is a powerful tool for categorizing individual’s weight in health and in disease. To the best of our knowledge, this is the first study that measures body mass index (BMI) and Peak expiratory flow rate (PEFR) for the lzon communities in Bayelsa State, Nigeria which has been exposed to harmful toxic polluted air through long standing oil and gas exploration and exploitation in the past four decades. PEFR values for the overall population as well as for the both genders fell within the ranges for the general, normal adult Nigerian populations3,5-7. In reference to these studies it was observed that the mean PEFR value fell within the lower limits of ranges for normal adult Nigerians and that for the general African descents when compared with Caucasians8,9. A probable explanation for the cause of the diminution in PEFR might be a reflection of cumulative effect of environmental associated air pollution from oil and gas flared- induced climatic changes, high temperature and high humidity prevalence as well as sedentary lifestyle which negatively impacted on the respiratory function. Increased environmental pollution, lack of physical activities and comparatively low socioeconomic progress, exposure to high ambient air temperature and high relative humidity10 has been attributed to be some of the causes of reduced respiratory functions (PEFR). Adiposity- the pattern of fat distribution has also been suggested as a significant predictor of decreased PEFR11. Table-1 Typical age, body mass index and peak flow expiratory rate values of the population, (Values are given as Mean ± Standard deviation, with range in parenthesis) Parameters Male (n=601) Female (n=532) Significant différence Z – TES T (p value) Age (yrs) 30.52 ± 11.79 (15 -89) 30.24 ± 13.50 (15 -80) no Peak expiratory flow rate (L/min) 408.78 ± 113.705 (130 – 670) 321.07 ± 77.83 (150 – 560) yes (0.01) Body Mass Index (kg/m 2 ) 25.23 ± 4.07 (16.14 – 40.56) 22.44 ± 4.84 (16.22 – 42.87) Yes ( 0.04) Research Journal of Recent Sciences ______________________________________________________________ ISSN 2277-2502Vol. 2(2), 28-32, February (2013) Res. J. Recent Sci. International Science Congress Association 30 Figure-1 A scatter plot showing the relationship between age and peak flow expiratory rate of the population Table-2 Categorization of subjects by body mass index and peak flow expiratory rate according to age groups (Values are given as Mean ± Standard deviation, with range in parenthesis) Parameters 20yrs 20 –29yrs 30 – 39yrs 40 – 49yrs 50 – 59yrs 60yrs ANOVA P-value Total Population : PEFR (L /min) (n=84) 327.14 ± 5.39 (200 – 470) (n= 634) 400.85±113.61 (200 – 670) (n=225) 350.80± 9.45 (150 – 620) (n=74) 331.89±64.22 (200 - 450) (n=52) 319.62±74.74 (220 – 510) (n=64) 229.69 ± 47.86 (130 – 315) 0.01 Male : PEFR (L/min) (n=42) 353.33 ± 75.31 (200 – 470) (n=324) 454.14±116.96 (200 – 670) (n= 141) 377.30± 74.68 (200 – 620) (n=36) 368.89±56.56 (200 - 450) (n=34) 319.62±74.74 (250 – 450) (n=24) 228.75 ± 56.65 (130 – 300) 0.01 Female : PEFR (L/min) (n=42) 300.95 ± 66.54 (200 – 470) (n=310) 345.16±77.80 (200 – 560) (n=84) 305.24± 65.83 (150 – 480) (n=38) 296.84±50.20 (200 - 400) (n=18) 280.00±44.98 (220 – 340) (n=40) 230.25±42.50 (150 – 310) 0.01 Total population : BMI (kg/m2) 22.09±3.23 (16.94 – 32.39) 25.32±4.44 (16.41 – 42.87) 26.38±4.24 (16.14 -40.90) 26.15±4.36 (16.22 – 36.05) 27.12±3.78 (20.40 – 36.51) 23.73±4.72 (16.71 – 38.16) 0.01 Table-3 Depicts peak expiratory flow rate according to the international classification of body mass index PARAMETER/ BMI Classification 18.5kg/m 2 Under weight n=40 18.5 –24.9 kg/m 2 Normal weight n=548 25 – 29.9 kg/m 2 Over weight n= 386 �30 kg/m 2 obese n=159 ANOVA P-value Entire Population PEFR (L/min) 296± 73.123 (150 – 470) 366.30±106.05 (130 – 660) 373.65± 107.46 (200 – 670) 374.47±114.98 (150 - 640) 0.02 yes Males: PEFR (L/min) 285.00± 46.18 (210 – 350) 402.58 ±110.70 (130 – 660) 417.31± 111.06 (200 – 670) 434.65±125.95 (200 - 640) 0.02 yes Females: PEFR (L/min) 303± 86.81 (150 – 470) 323.04±86.46 (180 – 560) 318.18 ± 71.29 (200 – 520) 325.91±76.84 (150 - 490) 0.58 No Research Journal of Recent Sciences ______________________________________________________________ ISSN 2277-2502Vol. 2(2), 28-32, February (2013) Res. J. Recent Sci. International Science Congress Association 31 Figure-2 Typical relationship between body mass index and peak flow expiratory rate for the entire population Further, there were statistically significant variations in PEFR and BMI with age. PEFR values significantly declined with increasing age consistent with previous studies11, which was largely attributed to the pattern of fat distribution in the body. Pearson correlation shows significant negative correlation between age and PEFR for the overall population and for both genders in contrast to the report which was largely young school children aged 5years-14 years. Correlation study shows positive relationship between PEFR and BMI for the overall population and for the both genders in contract to the studies in young Indian adults11. BMI for women fell within the spectrum of the normal adult body mass index cut off points, somewhere in between 20 - 22 kg/m which correspondingly reflected the relatively small body frame of female adults and may also be associated with the lower PEFR results. While BMI values observed for males was suggestive that they are likely predisposed to developing overweight for their body mass fell within the pre-obese spectrum of 25 – 27 kg/m2 ; and probably may also explain the relatively large body frames for male adults. The findings however, contrasts the report that weight trends are more pronounced among African Americans with 60% of African American men and 78% of African American women identified as overweight. Accordingly, 28.8% of men and 50.8% of African American women are considered obese12. Similarly, the findings also contrasted the report that obesity prevalence was higher in females13 but was consistent with high prevalence of overweight in males13. The observed BMI increase with age from the younger groups to 55-59.9 year group followed by decreased in age of the order of 60 years and above was in agreement with previous studies13. It has been suggested that body mass changes perhaps might probably be associated with genetic and environmental influences on eating and sedentary behaviours 14,15 which needed further studies. Generally, our results are consistent with other studies that normal lung function values are varied according to age, gender, BMI differences in PEFR; and there are lung function variations between different ethnic groups 8,13. Conclusion In conclusion, our study indicates that the inhabitants of Izon communities in the Niger Delta region of Nigeria may likely be predisposed to developing respiratory and pulmonary disorders related to prolonged exposure to potentially dangerous chemicals from oil and gas flared in the environment. Weight gain observed in males might probably be attributed to the influence of genetic factors related environmental influence on eating behaviour and sedentary activity which needed further studies. Our findings may serve as a baseline reference value for medical purposes in lzon communities in particular, the Niger Delta region of Nigeria. Acknowledgments We would like to thank the people of Okodi and Epebu communities for their co-operation and support in the course of this study. References 1.Magege E., Air pollution control in oil refinery, Napetar,9(2), 17-19 (1988) 2.Nwafor A., Peak expiratory flow rate of Nigerians in oil and fertilizer production environments, A preliminary study, Nig. J. Physiol. Sci,8(1-2) 122 (1992) Research Journal of Recent Sciences ______________________________________________________________ ISSN 2277-2502Vol. 2(2), 28-32, February (2013) Res. J. Recent Sci. International Science Congress Association 32 3.Nwafor A., A survey of peak expiratory flow rate and anthropometric characteristics of young Nigerians in Port Harcourt, Pecop J. Trop. Med. Health. 1(1), 23-29 (2004) 4.Jain P., Kavuru M.S., Emerman C.L. and Ahmad M., Utility of peak expiratory flow monitoring, Chest., 114, 861–876 (1998) 5.Ihekwaba A.E., Nwafor A. and Adienbo O.M., Lung function indices in primary and secondary sawmill workers in Port Harcourt, Afri. J. App. Zoo. Envrio. Bio,11, 101-105 (2009)6.World Health Organization: BMI Classification, WHO Global Database on Body Mass (2006)7.Ebomoyi M.I. and Iyawe V.I., Variations of peak expiratory flow rate with anthropometric determinants in a population of healthy adult Nigerians, Nig J. Phy. 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