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The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 60:350-354 (2005)
© 2005 The Gerontological Society of America

Relationship Between Lung Function and Physical Performance in Disabled Older Women

Crystal F. Simpson1,, Naresh M. Punjabi2, Linda Wolfenden3, Michelle Shardell4, David M. Shade2 and Linda P. Fried1

1 Center on Aging and Health and Division of Geriatric Medicine
2 Division of Pulmonary Medicine and Critical Care, The Johns Hopkins School of Medicine, Baltimore, Maryland.
3 Division of Pulmonary Medicine, Emory School of Medicine, Atlanta, Georgia.
4 Department of Biostatistics, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland.

Address correspondence to Crystal Simpson, MD, MHS, The Johns Hopkins University, Center on Aging and Health, 2024 East Monument Street, Suite 2-700, Baltimore, MD 21205. E-mail: cfsimpson{at}jhmi.edu


   Abstract
Top
 Abstract
Methods
 Results
 Discussion
 References
 
Background. Understanding the association between lung function and physical performance in disabled older women helps in determining the potential for prevention and treatment strategies to decrease disability. The aim of this study was to determine the association of lung function with objective and self-reported physical performance in community-dwelling disabled older women.

Methods. The Women's Health and Aging Study I consists of 1002 disabled community-dwelling women aged ≥65. Of these women, 840 underwent spirometry with determination of forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). Cross-sectional analyses included multivariate linear regression to assess the association between FEV1, FVC, FEV1/FVC, and the time to walk four meters after adjusting for confounders, including age, race, geriatric depression scale score, body mass index, muscle strength, osteoarthritis, smoking status, and cardiovascular disease. Multiple logistic regression was used to assess the association between FEV1,FVC, FEV1/FVC, and self-reported disability in physical performance.

Results. FEV1 was independently associated with time to walk 4 meters. For every 100 ml decrease in FEV1, there was a 0.15-second (95% confidence interval: 0.24 to 0.06) increase in time to walk 4 meters. There was an 8% increase in the prevalent odds of self-reported disability in physical performance for every 100 ml decrease in FEV1. FVC was also associated with physical performance measures. In contrast, FEV1/FVC was associated with objective but not subjective physical performance.

Conclusion. Decreasing lung function is independently associated with decrements in objective and self-reported physical performance in disabled older women.

Fifty-Five percent of older adults in the United States (aged ≥65 years) report having a physical disability (1). Along with the high prevalence of disability associated with aging, 26% of older persons rate their health as fair or poor (1). Physical disability has been shown to be associated with poor self-rated health, and often is a consequence of chronic conditions (2,3). This finding is supported not only by objective assessment of function but also by self-report. In fact, an estimated 28% of individuals between the ages of 65 and 74 years report a limitation in functional activity due to an underlying chronic condition (1).

Prominent among the chronic conditions that predispose elderly persons to disability is lung disease, including chronic obstructive pulmonary disease (COPD), asthma, and chronic bronchitis. These diseases are present in approximately 11% of older adults, and are independently associated with physical disability (4). In fact, COPD ranked 12th among all diseases in loss of disability-adjusted life-years in 1990, and is predicted to rank 5th by 2020 (4,5). Other studies (6,7) have also shown that decreased lung function independent of underlying lung disease can diminish physical performance in healthy older adults, as assessed by the 6- and 12-minute walk test.

Overall, studies to date have evaluated the relationship between lung function and physical function in relatively healthy community-dwelling adults who were not disabled or were, at most, mildly to moderately disabled. The independent impact of lung function on the physical performance of those who are already disabled, with multiple comorbidities, has not been well characterized. Data on the relationship between lung function and physical performance would serve as the basis for determining whether there are potential performance or quality-of-life benefits of optimizing lung function in disabled older adults with multiple comorbidities.

The objective of this study was to examine the cross-sectional association between lung function and physical performance in a sample of the most disabled community-dwelling older women; this association might provide the basis for interventions to prevent further decline in lung function in an already disabled population.


   METHODS
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 Abstract
 Methods
Results
 Discussion
 References
 
The current study is based on cross-sectional data collected in the Women's Health and Aging Study I, a prospective observational study of 1002 women aged ≥65 who were selected to represent the most disabled one third of older women living in the community. The study protocol was approved by the institutional review board at Johns Hopkins School of Medicine. The methods of the study have been previously described (8). Briefly, the participants were recruited from an age-stratified random sample of the Health Care Finance Administration's Medicare eligibility lists in Baltimore, Maryland (9). A total of 5316 women were sampled as eligible for screening; approximately 80% (4137) of these women were screened. One third of those screened (1409) were found eligible for the study, and of those who were eligible, 1002 agreed to participate in the study.

Eligibility required self-reported difficulty with tasks in two or more of four domains of function (described below) and a Mini-Mental State Examination (MMSE) score of ≥18. The four functional domains were as follows: mobility (e.g., walking two or three blocks); upper extremity function (e.g., raising arms above head); higher functioning tasks (e.g., preparing a meal); and basic self-care tasks (e.g., bathing) (9).

The baseline examination included spirometry; standardized measures of performance; determination of sociodemographics; administration of the Geriatric Depression Scale (GDS); determination of smoking status; review of adjudicated history of physician diagnosis of prevalent stroke, congestive heart failure (CHF), angina, myocardial infarction (MI), peripheral arterial disease (PAD), osteoporosis, and osteoarthritis (OA); and documentation of self-reported difficulty in physical performance (i.e., walking one-quarter mile, walking up 10 stairs, lifting 10 pounds, and shopping). Grip strength and hip flexion strength were obtained using a dynamometer (8).

Of the 1002 women in the study, 840 underwent spirometry testing at baseline with measurements of forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). Of the 162 women without spirometry, 142 were excluded for medical or safety reasons, 9 refused, 2 were unable to perform the forced expiratory maneuver, 2 were physically unable to cooperate, and 7 were excluded due to equipment failure. Analysis comparing participants with and without spirometry showed that women without spirometry were more likely to be older, less educated, to have lower income, lower cognition, and to be African American.

Measures of Lung Function
The techniques for measuring FEV1 and FVC have been previously described (9). Briefly, a PJ5 spirometer (Burdick Inc., Deerfield, WI) with pneumotachograph was connected to an IBM-compatible computer (Interland, Inc., Atlanta, GA). The software for spirometry was developed by the National Institute for Occupational Safety and Health (NIOSH). Nurses who conducted the examination had received training and certification in a NIOSH-approved course on spirometry. Participants with bronchodilators were told not to use them for 6 hours prior to testing. The predicted values for spirometry testing were published by Knudson and colleagues (9). Readings were reviewed by the NIOSH reading center. Field technicians sought to obtain three acceptable spirograms (FEV1and FVC within 5%) using the American Thoracic Society Criteria Guidelines (10). Of the 840 participants who underwent spirometry, 639 participants completed acceptable spirograms. Readings deemed "not acceptable" were usually the result of a participant's inability to sustain forced expiration after repeated attempts. Nevertheless, the measured FEV1 and FVC values in these participants represent their best effort, and were included in the current study. In accordance with American Thoracic Society standards, we elected to analyze the highest FEV1 and FVC for each of the 840 participants so as to not exclude those most ill or disabled, and thus to provide a representative view of the true relationship between lung function and physical performance in the disabled older adult. Sensitivity analyses with and without these participants did not show any significant differences in the overall inferences. Due to missing responses for potential confounders, however, spirograms for only 690 participants were included in the current analysis.

Measures of Physical Performance
Participants were asked to walk a standardized 3- or 4-meter course at their usual and rapid paces (9). If the participant's house did not have adequate space for a 4-meter course, then a 3-meter course was used (n = 85). The participant was asked to stand with both feet at the starting line and begin walking on verbal command. The participants could also use a walking aid if necessary. Their time to complete the first meter and three or four meters was measured to 0.01 seconds. The average values for the one and three or four meters were used for the analysis. However, the rapid-pace walk test was only performed once. Analyses were performed with and without the 85 participants, and the interpretation of the analysis did not change (results not shown). Therefore, the results in this paper include those of the participants who walked 3 or 4 meters.

Data Analysis
The prevalence of self-reported limitation in mobility and chronic diseases was determined for the 840 women who underwent spirometry testing. Chi-square analysis was used to assess the differences in education, disability, income, and race between the participants who did and did not undergo spirometry testing (11). Multivariate linear regression models were used to assess the relationships between FEV1, FVC, and FEV1/FVC and the time to complete the 1- and 4-meter walks at usual and rapid paces. The models were adjusted for age, race, stroke, CHF, angina, MI, PAD, osteoporosis, OA, GDS, smoking status, grip and hip flexor strength, and body mass index (10). The covariates were chosen due to their known associations with disability. Multivariate logistic regression models were used to determine the relationship of FEV1, FVC, and FEV1/FVC with self-reported limitation in mobility; these models were adjusted for the aforementioned covariates. Each variable of self-reported limitation in mobility difficulty was analyzed separately. A p value of ≤.05 was considered statistically significant. All analyses were performed using Stata 6.0 (STATA Corporation, College Station, TX).


   RESULTS
Top
 Abstract
 Methods
 Results
Discussion
 References
 
Of the 840 women in the Women's Health and Aging Study I who underwent spirometry testing, 73% were Caucasian. The mean age was 78 years and the mean MMSE score was 26. The frequencies of chronic diseases ranged from 7% (stroke) to 38% (knee OA). Approximately 31% of the participants were considered to have lung disease, and of that subset, 54% had COPD. Over half of the participants had never smoked. Approximately 4% were on bronchodilator therapy, and 72% of those with COPD were using albuterol inhalers. The mean FEV1 and FVC were 1.40 liters (range, 0.15–2.85) and 1.94 liters (range, 0.17–3.88). The mean FEV1/FVC ratio was 73.6%. The mean FEV1 for those who were prescribed albuterol therapy was 0.93 liters versus 1.41 liters for those who were not taking albuterol (Table 1).


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  		Table 1. Demographic Characteristics of Women Who Underwent Spirometry (N = 840).

 
The average time for the performance measures were as follows: 1 meter at usual pace, 3.0 seconds (range, 0.8–36.8); 4 meters at usual pace, 9.0 seconds (range, 2.1–48.3); 1 meter at rapid pace, 1.8 seconds (range, 0.5–10.1); and 4 meters at rapid pace, 5.8 seconds (range, 1.3–39.5) (see Table 2).


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  		Table 2. Baseline Characteristics (N = 840).

 
Lung Function and Objective Physical Performance
In multivariate linear regression analyses, FEV1, FVC, and FEV1/FVC were each independently associated with walking times in separate analyses after adjusting for body mass index, age, stroke, CHF, angina, MI, PAD, osteoporosis, OA, GDS total score, grip and hip flexor strength, smoking status, and race. An increase in FEV1 of 100 ml was associated with decreases of 0.03 seconds in time to walk one meter at a usual pace, 0.15 seconds to walk four meters at a usual pace, 0.03 seconds to walk one meter at a rapid pace, and 0.10 seconds to walk four meters at a rapid pace.

Similar results seen for the relationship of FVC and FEV1/FVC with walking times, after adjusting for potential confounders. For both FVC and FEV1, the greatest differences were seen in the 4-meter rapid walk (Table 3). Increasing age, race, CHF, OA, grip strength, and stroke were also independently associated with time to walk 4 meters (results not shown).


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  		Table 3. Relationship Between Lung Function and Objective Measures of Physical Performance.

 
Lung Function and Self-Reported Physical Performance
We then assessed evidence for the association of lung function measures with self-report of physical performance, as indicated by perceived difficulty in performing four physical performance tasks in four separate models. In multivariate logistic regression analyses, a significant and negative association was observed between FEV1 and self-reported measures of physical performance. Those who had a 100 ml increase in FEV1 were 8% less likely to report difficulty walking a quarter mile and 5% less likely to report difficulty lifting 10 pounds independent of several confounders. They were also 4% less likely to report difficulty in walking up 10 steps or shopping. However, these changes were not statistically significant. Similar results were also seen for the association between FVC and self-reported measures of physical performance independent of several confounders. The association of FEV1/FVC with self-reported physical performance was significant for walking a quarter mile. Participants with a higher FEV1/FVC ratio were 1% less likely to report difficulty walking a quarter mile. However, FEV1/FVC was not associated with difficulty in climbing 10 steps, lifting 10 pounds, or shopping (Table 4).


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  		Table 4. Relationship Between Lung Function and Self-Reported Measures of Physical Performance.

 

   DISCUSSION
Top
 Abstract
 Methods
 Results
 Discussion
References
 
The results of the study demonstrate that, among the most disabled community-dwelling older women, higher lung function as measured by FEV1, FVC, and FEV1/FVC was independently associated with a decrease in walking times over a 4-meter course. This difference in walking pace could have a significant impact on a disabled person's ability to perform certain tasks, such as crossing the street in sufficient time, with attendant improvements in their independence and quality of life. In addition to decrements in objective performance, the results also indicate that older women with lower lung function report greater difficulty in performing functional tasks.

Previous studies have shown an association between FEV1 and mortality (12) and between FEV1, FVC, FEV1/FVC, and physical performance (6,7). However, there has been conflicting evidence as to an association between FEV1 and self-reported disability (5). This difference could be attributed, in part, to the differences in methodology to ascertain physical function. For example, asking about activities of daily living instead of mobility-related activities could lead to differences in the associations found because of different levels of energy expenditure required.

The Lung Health Study, which assessed participants with COPD, revealed a reduction in the rate of decline of lung function in those who stopped smoking for a period of 5 years. An initial benefit in increased FEV1 at 1 year was observed for those who used ipatropium bromide, although this benefit did not last for the total period of 5 years (13). The participants in this study were, in general, younger and healthier than were the participants in our study. Perhaps in the most disabled population, an improvement at one year either through smoking cessation or medication use may be beneficial to a patient's perception of mobility and quality of life, even if there is no overall improvement during a longer follow-up period.

This study addresses the independent role that lung function plays in both objective and self-reported performance in adults who are already disabled. By describing the cross-sectional association between lung function and physical function in disabled older adults, the current study highlights the need for stabilizing or improving lung function to retard the progression of disability in older adults. The major implications of this study are that, in individuals with preexisting disability, every effort should be made to maximize lung function. Programs that minimize deterioration of lung function, such as bronchodilators, pulmonary rehabilitation, and smoking cessation, should not be overlooked.

Although our results were statistically significant for the association between lung function and self-reported physical performance, the relationships showed minimal clinical significance (i.e., 1%–8% improvement). This may be because, in the older adult population, self-report of difficulty is related to a number of medical comorbidities. The severity of these other medical conditions might lead the patient either to modify the physical performance tasks or to cease performing them without assistance, thereby masking the independent association of lung function with self-report of physical performance difficulty.

There are several limitations of this study. First, the cross-sectional design limits the scope of causal inferences on the impact of lung function and physical performance. Second, although the presence of medical comorbidities was assessed to control for the potential of confounding, we did not assess the severity of these conditions.

Nevertheless, the current study has several important strengths. First, to our knowledge, this is the first study to assess the independent association between lung function and physical performance, both by objective and self-reported measures, in disabled community-dwelling older women. Second, the potential for rigorous adjustment due to several measured covariates (e.g., stroke) was examined and found not to alter the relationship. Moreover, given that the study sample was randomly chosen from a representative population of older women increases the generalizability of these results.

Summary
With the aging of the U.S. population and the increase in the number of disabled older community-dwelling adults, it is important to identify and assess interventions that can ensure that these individuals maintain good quality of life. The results of this study demonstrate a cross-sectional independent association between lung function and mobility in older, disabled, community-dwelling women. They provide the foundation for future interventional studies that can assess whether the specific treatment programs (i.e., bronchodilator use and smoking cessation) improve mobility and quality of life of older disabled adults.


   Acknowledgments
 
This study was supported by contracts NO1-AG-1-2112 and T32AG00247 from the National Institute on Aging and the John A. Hartford Foundation/American Federation of Aging Research.

Abstract was presented at the Gerontological Society of America Meeting, November 2002.


   Footnotes
 
Decision Editor: John E. Morley, MB, BCh

Received September 2, 2003

Accepted November 13, 2003


   References
Top
 Abstract
 Methods
 Results
 Discussion
 References
 

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