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Abstract

This study aimed to measure the levels of physical activity (PA) in people with dust-related pleural and interstitial lung diseases and to compare these levels of PA to a healthy population. There is limited data on PA in this patient population and no previous studies have compared PA in people with dust-related respiratory diseases to a healthy control group. Participants with a diagnosis of a dust-related respiratory disease including asbestosis and asbestos related pleural disease (ARPD) and a healthy age- and gender-matched population wore the SenseWear^® Pro3 armband for 9 days. Six-minute walk distance, Medical Outcomes Study 36-item short-form health survey and the Hospital Anxiety and Depression Scale were also measured. Fifty participants were recruited and 46 completed the study; 22 with ARPD, 10 with dust-related interstitial lung disease (ILD) and 14 healthy age-matched participants. The mean (standard deviation) steps/day were 6097 (1939) steps/day for dust-related ILD, 9150 (3392) steps/day for ARPD and 10,630 (3465) steps/day for healthy participants. Compared with the healthy participants, dust-related ILD participants were significantly less active as measured by steps/day ((mean difference 4533 steps/day (95% confidence interval (CI): 1888–7178)) and energy expenditure, ((mean difference 512 calories (95% CI: 196–827)) and spent significantly less time engaging in moderate, vigorous or very vigorous activities (i.e. >3 metabolic equivalents; mean difference 1.2 hours/day (95% CI: 0.4–2.0)). There were no differences in levels of PA between healthy participants and those with ARPD. PA was reduced in people with dust-related ILD but not those with ARPD when compared with healthy age and gender-matched individuals.

Keywords

Asbestosis interstitial lung disease diffuse pleural thickening physical activity

Introduction

The global epidemic of asbestos-related diseases and the occurrence of other dust-related respiratory diseases continue to have widespread ramifications, with some asbestos-related diseases now pandemic.¹ People with these diseases may experience respiratory symptoms, including dyspnoea, similar to other chronic respiratory diseases,^2
–4 and may have reduced exercise capacity.^5,6 The impact of asbestos-related diseases and other dust-related respiratory diseases on physical activity (PA) is unknown.

PA in older adults, with or without a chronic disease, is important in maintaining health. The extensive benefits of PA for many chronic diseases, including chronic obstructive pulmonary disease (COPD), have been outlined.⁷ For example, higher levels of PA in COPD have been associated with physiological benefits including a higher peak oxygen uptake, diffusing capacity for carbon monoxide (D_LCO) and expiratory muscle strength.⁸ In contrast, lower levels of PA in people with COPD have been associated with increased hospitalizations, reduced quality of life and increased morbidity and mortality.^9
–11 People with chronic respiratory diseases, including those with COPD and people awaiting lung transplantation, have been shown to be markedly inactive with considerable time spent in sedentary behaviour.^10,12,13 Whilst PA levels have been measured in people with other interstitial lung diseases (ILDs), no studies have examined PA levels specifically in people with dust-related respiratory diseases compared with a healthy control group.

The primary aim of this study was to measure PA in people with asbestos related pleural disease (ARPD) and dust-related ILDs and to compare these levels of PA with an age- and gender-matched healthy population. We hypothesized that people with ARPD and dust-related ILD would have reduced PA levels compared with healthy age-matched controls. The secondary aim was to examine the relationships between PA and measures of health-related quality of life (HRQoL) in people with ARPD and dust-related ILD.

Methods

Study design and participants

The study was a prospective observational study conducted between February 2009 and May 2012. Participants with a dust-related respiratory disease were recruited through the Workers’ Compensation Dust Diseases Board (DDB) of New South Wales and through respiratory physicians. People were eligible to participate if they had a medical diagnosis of a non-malignant dust-related pleural or interstitial respiratory disease including asbestosis, silicosis and ARPD (defined as diffuse pleural thickening and/or rounded atelectasis). Diagnosis had been established prior to enrolment into the study by the participant’s respiratory physician or by the DDB Medical Authority, which is a panel of respiratory physicians with specialist knowledge in occupational lung disease. The diagnostic process included an occupational history, clinical examination by a physician, radiological findings on chest X-ray and computed tomography scans and lung function results.¹⁴ Participants with a dust-related respiratory disease were divided into two cohorts, ARPD and dust-related ILD. Healthy participants aged between 60 years and 90 years were recruited through advertisement in the community.

People were excluded from the study if they had mesothelioma, discrete parietal pleural plaques as their only manifestation of dust exposure, cardiovascular, neurological or orthopaedic conditions limiting exercise performance, could not understand English or had participated in a pulmonary rehabilitation programme within the last 12 months. For the healthy cohort, participants were excluded if they had a chronic respiratory disease, or other relevant comorbidity including cardiovascular, neurological or orthopaedic conditions limiting exercise performance.

The study was approved by the Human Research Ethics Committee of Sydney South West Area Health Service and all participants gave written informed consent. The study was part of a larger trial registered with the Australian and New Zealand Clinical Trials Registry (ANZCTR12608000147381).

Outcome measures

The primary outcomes for the study were PA measured by an activity monitor including steps per day, daily total energy expenditure (EE), daily active EE and time spent in moderate, vigorous or very vigorous activities per day. Secondary outcomes were six-minute walk distance (6MWD), HRQoL measured by the Medical Outcomes Study 36-item short-form health survey (SF-36) Physical Functioning, Role Physical and Vitality scores and the SF-36 Physical Component Summary, anxiety and depression measured by the Hospital Anxiety and Depression Scale (HADS) and dyspnoea measured by the modified Medical Research Council (MMRC) dyspnoea scale.

Participants attended one day of testing at Royal Prince Alfred Hospital, Sydney, Australia, which included the six-minute walk test, SF-36 questionnaire, HADS and pulmonary function tests. On this day the activity monitor was fitted and written instructions given to the participant.

Pulmonary function tests

All participants performed spirometry (SensorMedics, Yorba Linda, California, USA) according to standard protocols.¹⁵ Results of the forced expiratory volume in one second (FEV₁) and forced vital capacity are expressed as a percentage of the predicted values.¹⁶ The participants with ARPD and dust-related ILD also performed measurements of lung volumes (via body plethysmography) and D_LCO.

Physical activity

PA was measured using an activity monitor (SenseWear^® Pro3 Armband (SWA), BodyMedia, Pittsburgh, Pennsylvania, USA), which incorporated a biaxial accelerometer and sensors for skin temperature, heat flux and galvanic skin resistance. Participants wore the SWA on the triceps of the right arm for nine consecutive days from the day of testing. The first and last days were not included in the data collection as only data from a complete 24-hour period were collected.

Participants were instructed to wear the SWA continuously, remove it only during showering or swimming, and were advised to remove the SWA in the event of any adverse reaction. Written instructions for wearing the SWA were provided to remind participants of correct wear. Compliance was set at a minimum wear time of ≥85% per day (which equated to a minimum of 20 hours per day) for at least four days.

Measures of PA including steps per day, daily total EE, daily active EE (i.e. total EE >3 metabolic equivalents (METs)) and time spent in moderate, vigorous or very vigorous activities per day (i.e. >3 METs) were recorded. Measures of PA were examined by the SenseWear Professional software Version 6.1.

Exercise capacity

Participants performed two six-minute walk tests according to the American Thoracic Society guidelines¹⁷ with tests separated by a minimum of 30 minutes rest. Throughout both tests standardized instructions and encouragement were given. The best six-minute walk test result was used for analysis.

HRQoL, anxiety and depression

Participants completed the SF-36 and HADS.^18,19 The HADS was used to measure the levels of anxiety and depression in study participants, with scores greater than eight in either anxiety or depression indicative of clinically relevant symptoms. The SF-36 is a generic HRQoL questionnaire examining eight health concepts covering physical and mental health. SF-36 scores were calculated using the QualityMetric Health Outcomes^TM Scoring Software 2.0.

Dyspnoea

The MMRC dyspnoea scale was used to assess levels of dyspnoea.²⁰

Statistical analysis

Statistical analysis was performed on PASW-Windows (release 18.0; PASW, Chicago, Illinois, USA). All baseline data are expressed as mean (SD). One-way analysis of variance (ANOVA) was used to compare groups and, if significant, an independent group t test was used to determine the size of effect between groups (ARPD, dust-related ILD and healthy control group). To assess the relationships between PA and HRQoL, Pearson’s correlation coefficients were used. The level of significance was set at a p value of <0.05. An initial sample size for the study was not calculated to estimate power. Post hoc, based on our participant numbers and on a recent study in COPD reporting an SD of 2565 steps per day for step count,²¹ we have determined that the sample size of our study was powered to detect a difference between the healthy group and the dust-related ILD group of 3300 steps per day or greater and between the ARPD group and the dust-related ILD group of 2900 steps per day or greater but was not powered to detect a difference between the ARPD group and the healthy group (statistical power of 80% with a 5% significance level).

Results

Fifty male participants were screened for inclusion into the study. Of this group, 48 participants met the inclusion criteria and were recruited. Twenty-four participants had ARPD, 10 had dust-related ILD (asbestosis: 6; silicosis: 3; and mixed-dust pneumoconiosis: 1) and 14 were healthy controls. The reason for non-inclusion of two participants was the presence of pleural plaques with no evidence of asbestos related pleural or parenchymal disease (one participant) and known metal allergy with possible allergy to the SWA sensors (one participant). An additional two participants with ARPD were excluded from the data analysis as the SWA was worn for less than four complete days. Reasons for this non-compliance with the SWA were skin irritation (one participant) and subjective reports of headache (one participant).

Participant characteristics

Characteristics of participants who completed the data collection are shown in Table 1. There were no statistically significant differences in age or body mass index between participants with ARPD, participants with dust-related ILD and the healthy control group. ANOVA showed that there were statistically significant differences in 6MWD (p = 0.001), MMRC (p < 0.0001), FEV₁ (p < 0.005), SF-36 vitality score (p = 0.03) and the HADS depression score (p = 0.01) across groups (Table 1). For the outcomes that were significant in the ANOVA, where the difference between the groups is, is presented in Table 1.

Table 1.

Characteristics, lung function tests, exercise capacity, HRQoL and anxiety and depression of the study participants.

	Dust-related ILD group (n = 10; mean (SD))	ARPD group (n = 22; mean (SD))	Healthy group (n = 14; mean (SD))	ANOVA p value comparing groups
Age (year)	72 (10)	71 (5)	70 (6)	0.71
Height (cm)	170 (7)	174 (5)	173 (5)	0.11
Weight (kg)	77 (12)	84 (12)	85 (10)	0.19
BMI (kg/m²)	27 (3)	28 (3)	28 (3)	0.44
FVC (% predicted)	98 (19)	82 (20)	88 (10)	0.06
FEV₁ (% predicted)	92 (12)	73 (21)	88 (8)	0.005^a,b,c
FEV₁/FVC (% predicted)	95 (14)	90 (15)	101 (9)	0.066
TLC (% predicted)	84 (15)	81 (20)	–	0.61
VC (% predicted)	103 (20)	86 (22)	–	0.05
RV (% predicted)	65 (15)	80 (32)	–	0.16
FRC (% predicted)	78 (24)	80 (23)	–	0.78
D_LCO (% predicted)	49 (13)	59 (13)	–	0.049^a,b
KCO (% predicted)	65 (16)	86 (16)	–	0.002^a,b
MMRC	1 (1)	1 (1)	0 (0)	<0.0001^a,b,c,d
6MWD (m)	462 (102)	483 (68)	584 (96)	0.001^a,c,d
SF-36 PF	60 (20)	72 (23)	84 (24)	0.05
SF-36 RP	73 (38)	80 (34)	82 (33)	0.79
SF-36 Vitality	62 (18)	74 (14)	78 (13)	0.03^a,b,d
SF-36 PCS	45.5 (8.0)	48.1 (9.9)	49.4 (7.9)	0.58
SF-36 MCS	50.8 (9.4)	55.2 (7.7)	57.6 (4.1)	0.09
Anxiety	5 (2)	4 (4)	4 (3)	0.41
Depression	5 (3)	2 (2)	2 (1)	0.01^a,b,d

ILD: interstitial lung diseases; n: number; SD: standard deviation; ARPD: asbestos related pleural disease; cm = centimetre; kg = kilogram; BMI: body mass index; m = metre; FVC: forced vital capacity; FEV₁: forced expiratory volume in one second; TLC: total lung capacity; VC: vital capacity; RV: residual volume; FRC: functional residual capacity; D_LCO: diffusing capacity for carbon monoxide; KCO: carbon monoxide transfer coefficient; MMRC: modified Medical Research Council dyspnoea scale; 6MWD: six-minute walk distance; SF-36: Medical Outcomes Study 36-item short-form health survey; PF: physical functioning; RP: role physical; PCS: physical component score; MCS: mental component score; ANOVA: analysis of variance; ^a p < 0.05: ANOVA comparing the three groups.

^bSignificant difference between the asbestos related pleural disease group and dust-related interstitial lung disease group.

^cSignificant difference between the healthy group and the asbestos related pleural disease group.

^dSignificant difference between the healthy group and the dust-related interstitial lung disease group.

Compared to the ARPD group, the dust-related ILD group had lower 6MWD, HRQoL, D_LCO and carbon monoxide transfer coefficient (KCO) and higher depressions scores. The ARPD and the dust-related ILD groups had significantly lower 6MWD than the healthy control group. HRQoL was not significantly different between the ARPD group and healthy control group.

High-resolution computed tomography scans showed that two participants with dust-related ILD had evidence of concomitant COPD. The smoking history (mean (SD)) was 11 (15) pack years for participants with ARPD, 31 (28) pack years for participants with dust-related ILD and 11 (24) pack years for the healthy control group.

PA in daily life

Daily PA characteristics of all groups are presented in Table 2. There were no differences between groups for SWA compliance. For the outcomes that were significant in the ANOVA, the between group differences are shown in Table 3. There was a significant decrease in all PA outcomes when the dust-related ILD group was compared with the healthy group (all p < 0.05) and when the dust-related ILD group was compared with the ARPD group (all p < 0.05; Table 3). There were no differences in measures of PA between the ARPD group and the healthy control group (Table 3).

Table 2.

PA of study participants.

	Dust-related ILD group (n = 10; mean (SD))	ARPD group (n = 22; mean (SD))	Healthy group (n = 14; mean (SD))	p Value ANOVA
Total days worn	6.5 (1)	6.2 (1)	6.4 (1)	0.65
Daily compliance (%)	98 (1)	98 (1)	97 (2)	0.11
Steps/day	6097 (1939)	9150 (3392)	10630 (3465)	0.01^a
EE (cal/day)	2199 (293)	2267 (447)	2711 (300)	0.003^a
Active EE (>3.0 METs; cal/day)	283 (189)	608 (355)	709 (340)	0.01^a
Time spent >3.0 METs (hours/day)	1.0 (0.6)	1.8 (0.8)	2.2 (1.2)	0.01^a

ILD: interstitial lung diseases; n = number; SD: standard deviation; ARPD: asbestos related pleural disease; EE: energy expenditure; cal = calorie; MET: metabolic equivalent.

^a p < 0.05: comparing all groups.

Table 3.

Mean differences between groups in PA outcomes.

	ARPD group- Dust-related ILD group Mean difference (95% CI)	Healthy group- ARPD group Mean difference (95% CI)	Healthy group- Dust-related ILD group Mean difference (95% CI)
Steps/day	3053 (616, 5489)	1480 (−704, 3664)	4533 (1888, 7178)
EE (cal/day)	468 (177, 759)	44 (−217, 304)	512 (196, 827)
Active EE (>3.0 METs; cal/day)	325 (77, 573)	101 (−121, 323)	426 (157, 695)
Time spent >3.0 METs (hours/day)	0.8 (0.1, 1.5)	0.4 (−0.2, 1.0)	1.2 (0.4, 2.0)

ARPD: asbestos related pleural disease; ILD: interstitial lung disease; CI: confidence interval; cal = calorie; EE: energy expenditure; MET: metabolic equivalent.

Correlations between PA and HRQoL

A significant correlation was demonstrated between steps per day and the SF-36 Role Physical domain in people with ARPD. No other correlations between measures of PA and HRQoL were demonstrated (Table 4).

Table 4.

Relationships between measures of PA and HRQoL scores (r values).

Variable	Dust-related ILD (n = 10)		ARPD (n = 22)
	Steps/day	Active EE ((>3.0 METs)/day)	Steps/day	Active EE ((>3.0 METs)/day)
SF-36 PF	0.387	0.392	0.331	0.130
SF-36 RP	−0.350	−0.250	0.466^a	0.231
SF-36 Vitality	−0.140	0.344	0.220	0.038
SF-36 PCS	0.205	0.487	0.267	0.084
HADS Anxiety	−0.141	−0.493	0.222	0.193
HADS Depression	0.270	−0.257	0.016	0.054
MMRC	−0.479	−0.366	−0.316	0.028

ILD: interstitial lung disease; n: number; ARPD: asbestos related pleural disease; EE: energy expenditure; MET: metabolic equivalent; SF-36: Medical Outcomes Study 36-item short-form health survey; PF: physical functioning; RP: Role Physical; PCS: physical component summary; HADS: Hospital Anxiety and Depression Scale; MMRC: modified Medical Research Council dyspnoea scale.

^a p < 0.05.

Discussion

This is the first study to investigate PA in people with ARPD and dust-related ILD compared with a healthy control group. The main finding of this study was that PA in people with dust-related ILD was reduced compared with both a healthy age- and gender-matched control group and people with ARPD. Our data also showed no differences in levels of PA between the ARPD group and the healthy control group.

The mean daily step count of 6097 steps/day in the dust-related ILD group was lower than the daily step count in the ARPD group and the healthy control group. In addition, the step count in the dust-related ILD group was below the range of 7000–10,000 daily steps recommended for healthy older adults and lower than the range recommended for individuals living with a chronic illness (6500–8500 steps per day).²² However, it is difficult to compare this latter recommendation to the dust-related ILD group as it is based on cardiac patients and few other recommendations are available on daily step count in people similar to those in the present study. In studies of people with COPD, with disease severity ranging from mild to severe, mean daily step counts varied from 4725 steps/day to 5584 steps/day.^11,23 A daily step count of less than 4580 steps has been associated with severe physical inactivity.²⁴ Based on step count, in our study the dust-related ILD group was less active than the healthy control group but more active than that reported for people with COPD and would not be categorized as severely physically inactive. In addition, whilst the dust-related ILD group had the lowest levels of PA in our study, these levels of PA were not as low as those reported in people with advanced ILD.¹³

There were significant reductions in all measures of PA in the dust-related ILD group compared with the ARPD group. ARPD is characterized by fibrosis to the parietal pleura, which may extend to the visceral pleura but there is no pulmonary parenchymal fibrosis, as seen in dust-related ILD.²⁵ As a result, KCO was maintained in the ARPD group, whereas in the dust-related ILD group, in whom there was parenchymal fibrosis, D_LCO and KCO were reduced. Despite similarities in lung volumes and MMRC dyspnoea scores in the ARPD and dust-related ILD groups, the presence of parenchymal fibrosis and consequent reductions in D_LCO and KCO in the dust-related ILD group may be a factor in reduced PA levels in this group.

The restrictive nature of the dust-related ILDs is demonstrated by the residual volume and functional residual capacity, despite preserved vital capacity. High-resolution computed tomography scans confirmed that only two participants with dust-related ILD had evidence of concomitant COPD. Therefore, the findings of this study are specifically related to people with dust-related ILD and are not confounded by co-existing COPD.

A moderate correlation was found between the SF-36 domain of Role Physical and steps per day in people with ARPD, suggesting that this domain may provide some information relating to daily activity levels. However, the lack of consistent relationships between PA and the other SF-36 domains in the ARPD and dust-related ILD groups, highlight the importance of measuring PA and HRQoL as discreet, patient-important outcome measures, despite the SF-36 having a physical component to the questionnaire.

Participants with ARPD and dust-related ILD showed excellent compliance wearing the SWA with a mean daily compliance of 98%. This highlights the feasibility of objectively measuring PA levels in this patient population. However, the accuracy of the SWA in participants with dust-related respiratory diseases is unknown. In people with COPD, it has been shown that measurement of steps using the SWA has been underestimated in people walking at slow speeds.²⁶ It is possible that the step count of participants with dust-related ILD was underestimated if they had slow walking speeds. However, based on the 6MWD, which equated to a walking speed of 3.6 kilometres per hour or higher in the dust-related ILD group, measurement error due to slow walking speeds is unlikely. Further studies examining the accuracy of the SWA in people with ARPD and dust-related ILD are needed.

For people with dust-related ILD, the low PA levels may be reversible. Immediately following exercise training in a combined cohort of people with ARPD and dust-related ILD, PA levels increased.²⁷ However, the improvements in PA were very small in the longer term. The improvements in PA specific to either people with dust-related ILD or ARPD remain unknown. In people with COPD, a meta-analysis has demonstrated a small increase in PA after exercise training.²⁸ In addition, motivational support and exercise counselling programs, or a combination of pulmonary rehabilitation, PA counselling and pedometer feedback, have resulted in improved levels of PA in people with COPD.^29,30,31 With limited treatment options for people with dust-related ILD, and the important health benefits associated with higher levels of PA shown in other populations, these programs should be explored further in this patient population.

The main limitation of this study was the small sample size which limits the generalizability of the findings to all people with ARPD or dust-related ILD. Secondly, as participants with dust-related respiratory diseases were not on oxygen therapy, the findings of this study cannot be generalized to people with severe disease on oxygen therapy.

Conclusion

This is the first study to assess PA in people with ARPD or dust-related ILD compared with a healthy control group. PA levels were reduced in people with dust-related ILD compared with people with ARPD and healthy age- and gender-matched individuals. Since higher levels of PA are associated with health benefits in other chronic respiratory diseases, further studies should evaluate the effects of low PA on health outcomes and investigate specific interventions to increase PA in people with dust-related ILD.

Footnotes

Conflict of interest

The authors declared no conflicts of interest.

Funding

This study was partly funded by the Workers’ Compensation Dust Diseases Board (DDB) of New South Wales.

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Physical activity in people with asbestos related pleural disease and dust-related interstitial lung disease