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Brief Communication |
Address correspondence to Jong Weon Choi, M.D., Ph.D., Department of Laboratory Medicine, Inha University Hospital, 7-206, 3-ga, Shinheung-dong, Jung-gu, Inchon, 400-711, South Korea; tel 82 32 890 2503; fax 82 32 890 2529; e-mail jwchoi{at}inha.ac.kr.
Abstract
To investigate the association between respiratory function and basal metabolic rate (BMR), pulmonary function indices and BMR were measured in 251 elderly persons using a spirometer and a body composition analyzer. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were more strongly correlated with BMR (r = 0.48 and r = 0.43, p < 0.01) than with lean body mass (r = 0.36 and r = 0.35, p < 0.01) and waist-to-hip ratio (r = -0.29 and r = -0.32, p < 0.01) in elderly men. FVC and FEV1 in elderly men with BMR 
1390 kcal/day averaged 4.05 ± 0.56 L and 3.19 ± 0.45 L, which were significantly above the values (3.54 ± 0.51 L and 2.80 ± 0.42 L, p < 0.01) in men with BMR <1390 kcal/day. Prevalences of the subjects with elevated FVC or FEV1 were significantly higher in the group of men with BMR 1390 kcal/day than in those with BMR <1390 kcal/day (66.0% and 68.0% vs 28.3% and 33.9%, p < 0.01). No significant differences were observed between the postmenopausal women with BMR 1135 kcal/day and those with BMR <1135 kcal/day. In summary, respiratory function is more closely associated with BMR in elderly persons, compared to lean body mass, waist-to-hip ratio, or body fat mass, and these associations are stronger in men than in women.
(received 1 October 2003; accepted 8 October 2003)
Keywords: Respiratory function, basal metabolic rate, body composition, anthropometrics
Introduction
Elderly men and women tend to become more obese and their lung function declines with advancing age [1]. Age-related changes in pulmonary function are clinically relevant because impaired lung function is associated with increased mortality rates [2,3]. Weight gain is accompanied by a decrease in forced vital capacity (FVC) and forced expiratory volume in one sec (FEV1), and reduction of body weight leads to significant improvement in pulmonary function [4–6].
Body fat distribution is related to pulmonary impairment in elderly persons: a central pattern of fat distribution is negatively associated with respiratory function [7]. Abdominal and chest fat accumulation is related to a decrease of expiratory reserve volume in obese individuals, and airway resistance increases significantly with the degree of obesity [8].
Many studies have demonstrated associations between ventilatory dysfunction and excess weight or body fat distribution [4–8]. However, few studies have examined the relationship of ventilatory dysfunction with basal metabolic rate (BMR). In this study we investigated the associations of BMR, body composition, and anthropometrics with indices of pulmonary function in elderly men and in age-matched postmenopausal women.
Materials and Methods
Anthropometric parameters and body composition, including height, body weight, body fat mass, lean body mass, BMR, and waist-to-hip ratio (WHR) were measured in 251 non-smoking healthy adults. The subjects comprised 103 elderly men (median age = 61 yr, range = 57 to 64 yr) and 148 postmenopausal women (median age = 60 yr, range = 56 to 65 yr). Participants who had smoked <5–10 packs of cigarettes during their lifetime were defined as non-smokers [9]. Women were judged to have entered menopause when they had not menstruated for 12 mo prior to the investigation. The subjects were all Korean from middle-class families who had been screened in a routine health assessment program. Some individuals (n = 9) were excluded from this study: subjects who had postmenopausal hormone replacement therapy (n = 3), heart failure (n = 2), or chronic obstructive pulmonary diseases (n = 4). This study was approved by the Ethical Committee of Inha University Hospital, and informed consent was obtained from all subjects.
The subjects’ anthropometric characteristics were assessed by use of an 8-polar tactile-electrode impedance-meter, the body composition analyzer (InBody 3.0, Biospace, Seoul, Korea), which provides simultaneous measurements of body weight, lean body mass (or fat-free mass), total body water, regional fat deposit, and BMR, while the subject stands on the stainless steel electrode [10]. The InBody 3.0 system calculates BMR based on resting energy expenditure (REE) from the following equation: REE (kcal/day) = 370 + (21.6 x fat-free mass in kg), which explains 65–90% of the variation in BMR [11]. The precision of BMR and lean body mass measurements was determined in 30 elderly persons, each of whom was measured twice with a 1-week interval. The coefficient of variation (CV) of BMR measurements was <3.8%; the CV for lean body mass measurements was <4.1%. BMI was determined as body weight in kilograms divided by the square of the height in meters (kg/m2).
Spirometry was performed under standard conditions of ambient temperature, barometric pressure, and relative humidity. Measurements were made with a closed-circuit spirometer (MedGraphics CPFS/D BREEZE; Medical Graphics Corp, MN, USA) with the subjects sitting down and wearing a nose clip. Each subject performed 3 acceptable FVC maneuvers according to the American Thoracic Society recommendation [12]. The largest FVC and FEV1 values were recorded after examining the data from all the acceptable curves, even if they did not come from the same curve. All measurements and analyses were performed by the same investigator.
To compare the pulmonary function indices vs BMR, the subjects were assigned to 1 of 4 groups: elderly men with BMR <1390 kcal/day (n = 53) and those with BMR 1390 kcal/day (n = 50); postmenopausal women with BMR <1135 kcal/day (n = 78) and those with BMR 1135 kcal/day (n = 70). The prevalence of the subjects with increased pulmonary function in relation to the BMR was investigated. Elderly men with FVC >3.79 L or FEV1 >2.99 L and postmenopausal women with FVC >2.51 L or FEV1 >2.12 L were classsified as subjects with increased pulmonary function. The cutoff values of BMR, FVC, and FEV1 were determined provisionally based on the mean values in age- and gender-matched healthy individuals.
Data analyses were performed with the SAS 6.12 software package (SAS Institute Inc, Cary, NC). A non-parametric test (Mann-Whitney U test) was used to calculate the statistical significance of intergroup differences because the distributions of most of the analyzed variables were non-Gaussian. Correlation coefficients were calculated by Spearman’s method. All p values <0.01 were considered statistically significant.
Results and Discussion
This study demonstrates for the first time that BMR correlates more strongly with FVC and FEV1 in elderly persons than the well-known parameters, such as BMI, lean body mass, or WHR. Mean values of FVC and FEV1 in elderly men with BMR 1390 kcal/day were 4.05 ± 0.56 L and 3.19 ± 0.45 L, which were significantly higher than those in men with BMR <1390 kcal/day (3.54 ± 0.51 L and 2.80 ± 0.42 L, p < 0.01). FVC and FEV1 in postmenopausal women with BMR 1135 kcal/day averaged 2.62 ± 0.34 L and 2.23 ± 0.31 L, which were significantly higher than the values (2.41 ± 0.27 L and 2.03 ± 0.26 L, p < 0.01) in women with BMR <1135 kcal/day (Table 1
).
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). The significant elevations of FVC and FEV1 that were observed in the subjects with increased BMR, who showed no significant differences in age, body fat mass, or WHR, suggests that measurement of BMR may be valuable in assessing impairment of airway function, especially in elderly men.
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). These results suggest that pulmonary function is more closely associated with fat distribution than with the extent of total fat mass. It is conceivable that chest fat accumulation is related to inactive chest-wall compliance and that fat stored within the abdominal cavity may impede descent of the diaphragm.
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In conclusion, FVC and FEV1 were more strongly correlated with BMR than with total body fat, WHR, or lean body mass, suggesting that respiratory function is more closely associated with BMR, at least as compared to body fat, lean body mass, or WHR, in elderly men and women. Further studies regarding serum concentrations of hormones, behavioral habits, and physical exercise are needed to explain why BMR correlates so closely with pulmonary function indices in elderly subjects.
References
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