Cystic fibrosis (CF) is a hereditary, chronic respiratory illness in which patients suffer from recurrent bouts of infection causing frequent hospitalization [
A reliable patient-reported measure of HPA, independent of overall quality of life, could provide an early indication of patients who are at risk for CF-related morbidity. Physical activity questionnaires contain limited reliability and validity, as they are prone to recall bias [
The Life-Space Assessment (LSA) is a validated tool used to measure mobility patterns in geriatric patients [
The study was approved by the Emory Institutional Review Board. All participants provided written informed consent for participation in this study. Participants were recruited during outpatient clinic visits at the Emory University Adult Cystic Fibrosis Center in Atlanta, Georgia, between March 2011 and May 2012. Inclusion criteria for this study were a CF diagnosis, being clinically stable, and age ≥18 years. Participants were excluded if their clinic visit indicated need for hospitalization and/or acute exacerbation. Upon enrollment, subjects completed the LSA. Subjects completed the LSA monthly, either during clinic visits or by phone interview conducted by study investigators. Demographic and clinical characteristics were extracted from subjects’ medical records. Thirty-five participants were recruited for the study, out of which 27 completed the one-year follow-up visit.
Subjects were provided with a pedometer (New Lifestyles DIGI-WALKER SW-200, New-Lifestyles Inc., Lee’s Summit, Montana) that they were asked to wear for three consecutive days quarterly for one year. Three days has previously been reported to provide a sufficient estimate of weekly pedometer-assessed physical activity [
The LSA score is a measure of the frequency and independence of travel to different areas extending outward from one’s dwelling space during the previous four weeks [
Descriptive statistics were compiled. The average number of steps by pedometer and average LSA score were recorded at time of enrollment and over the course of the year. Pearson correlation analyses were used to assess the relationship between LSA scores and reported numbers of pedometer steps at baseline, as well as average one-year scores and steps, respectively. All statistical analyses were performed using the JMP Pro 10 software package (SAS Institute Inc., Cary, NC) and assumed a statistical significance value of
A total of 35 subjects consented to participation in this study. Twenty-seven subjects completed the one-year follow-up study visit. Dropouts were primarily due to inconvenience of monthly phone calls or inability to be contacted by phone. The study demographics for the 27 participants are presented in Table
Demographics of adult subjects with cystic fibrosis (
Age (years) | 32.15 ± 12.27 |
Race | |
White | 26 (96%) |
Black | 1 (4%) |
Sex | |
Male | 13 (48%) |
Female | 14 (52%) |
FEV1% predicted | 77.48 ± 22.60 |
Severity of lung disease by FEV1% | |
Very severe (<35%) | 2 (7%) |
Moderate to severe (35%–69%) | 8 (30%) |
Mild (>69%) | 17 (63%) |
BMI (kg/m2) | 23.46 ± 3.76 |
Mutation | |
ΔF508 homozygous | 12 (44%) |
ΔF508 heterozygous | 14 (52%) |
Others | 1 (4%) |
LSA score at enrollment | 90.39 ± 22.98 |
LSA score during study period | 91.94 ± 20.64 |
Pedometer steps at enrollment | 19452 ± 10118 |
Pedometer steps during study period | 20213 ± 11331 |
Reported as mean ± SD or
Subjects reported a mean (± SD) of 19,452 ± 10,118 steps over three days at enrollment and a mean of 20,213 ± 11,331 steps over three days recorded quarterly throughout the year. Subjects reported a mean (± SD) LSA score of 90.39 ± 22.98 out of 120 at baseline and a mean LSA score of 91.94 ± 20.64 recorded quarterly throughout the year (Table
The mean LSA score at enrollment was positively correlated with number of pedometer steps at enrollment (
Relationship between Life-Space Assessment score and steps recorded by pedometer at enrollment (a) and over 1 year (b). The Life-Space Assessment score was positively associated with physical activity as assessed by pedometers in adult subjects with cystic fibrosis at enrollment and after 1 year of follow-up.
Participants had a mean (± SD) FEV1% predicted of 77.48 ± 22.60%. Both enrollment and one-year average LSA were associated with lung function as measured by FEV1% predicted (
Both enrollment and one-year average pedometer steps were associated with FEV1% predicted (
In this study we examined the relationship between the LSA score and mobility assessed with pedometer step counts and the correlation of both measures with lung function. We found a significant positive correlation between the LSA score and number of pedometer steps, both at enrollment and throughout the year. Subjects with higher LSA scores reported a greater number of steps. This study provides preliminary validation of the LSA as an instrument to assess mobility and shows that greater mobility is associated with better lung function in patients with CF.
Physical activity is associated with maintenance or improvement of health status in patients with CF [
The LSA is short and concise and evaluates a subject’s mobility as measured in five zones extending outwards from the closest dwelling space. It has been validated as a predictor of health in the geriatric population, and studies have shown that subjects with a higher LSA score are more mobile [
In our study, LSA score was positively associated with the subjects’ lung function as measured by FEV1% predicted. Pedometer step counts were also associated with better lung function. Numerous reasons potentially explain our interrelationships between LSA score, pedometer step counts, and lung function. Greater step count could also reflect greater mobility, which may, in turn, indicate greater access to medical care (i.e., clinic visits), better treatment adherence, greater quality of life, and/or greater functioning in general, all of which would influence lung function [
A causal directionality cannot be determined with these studies. It is possible that impaired lung function precludes mobility and physical activity. Expression of defective CFTR in skeletal muscle may directly cause a reduction in work capacity and make patients with CF vulnerable to deconditioning [
Our data suggest that LSA is an efficient and effective instrument for evaluating the health status of a patient with CF. It provides information that can be shared among the multiple clinicians that participate in the care of a patient with CF, including physicians, nurses, dietitians, respiratory therapists, and social workers. It is taken for granted that all forms of physical activity are beneficial for patients with CF, to the extent that it was considered unethical to perform a study in which some patients would be randomized not to receive exercise training [
One limitation of this study was the small sample size. Additionally, this instrument is designed to assess habitual mobility, or “life-space,” rather than vigorous exercise or habitual physical activity, which the LSA does not capture. Thus it would not be used alone to fully measure physical activity or exercise, but it provides information that is less easily reported than the type, duration, and frequency of a formalized exercise program. Although the LSA was initially developed for the geriatric population, our previous study and the association of the LSA with pedometer counts in this study validate it for the CF population as well. Insofar as measuring physical activity for the purpose of this study, it may be argued that accelerometers are preferable to pedometers. However, we believe this difference is insignificant in this study because the LSA measures only mobility, which is comparable to number of steps by pedometer. Unlike pedometers, accelerometers are able to measure the vigor of the activity, but this is not a parameter assessed by the LSA and would not contribute substantially to our analysis. Furthermore, it has also been shown in community-dwelling older adults that step counts measured by pedometers and accelerometers are closely correlated [
The Life-Space Assessment score was associated with increased mobility, as assessed by pedometers, and higher lung function in nonhospitalized adults with CF. Future investigation is warranted to determine if the LSA tool can be used to examine the impact of mobility on long-term health outcomes in the CF population.
Cystic fibrosis
Cystic Fibrosis Questionnaire-Revised
Cystic Fibrosis Quality of Life
Forced expiratory volume in one second, percentage of predicted value
Habitual physical activity
Life-Space Assessment.
The authors report no conflict of interests.
This work was made possible by a student traineeship award from the Cystic Fibrosis Foundation to Aneesha Thobani and in part by grants from the National Institutes of Health Grants UL1 TR000454 (Atlanta Clinical and Translational Science Institute), K23 AR054334 (VT), T32 DK007298, and K01 DK102851 (JAA) and the CF Center grant to Emory University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the paper.