RationaleInformation concerning how climate and atmospheric pollutants affects physical activity in COPD patients is lacking and might be valuable in determining when physical activity should be encouraged.MethodsSeventy-three stable COPD patients recorded on daily diary cards worsening of respiratory symptoms, peak expiratory flow rate, hours spent outside the home and the number of steps taken per day. Pedometry data was recorded on 16,478 days, an average of 267 days per patient (range 29-658). Daily data for atmospheric PM10 and ozone (O3) were obtained for Bloomsbury Square, Central London from the Air Quality Information Archive databases. Daily weather data were obtained for London Heathrow from the British Atmospheric Data Archive.ResultsColder weather below 22.5 °C, reduced daily step count by 43.3 steps day per°C (95 % CI 2.14 to 84.4; p = 0.039) and activity was lower on rainy than dry days (p = 0.002) and on overcast compared to sunny days (p < 0.001). Daily step count was 434 steps per day lower on Sunday than Saturday (p < 0.001) and 353 steps per day lower on Saturday than Friday (p < 0.001). After allowance for these effects, higher O3 levels decreased activity during the whole week (-8 steps/ug/m3; p = 0.005) and at weekends (-7.8 steps/ug/m3; p = 0.032). Whilst, during the week PM10 reduced activity (p = 0.018) but not during the weekend.ConclusionsInactivity of COPD patients is greatest on cold, wet and overcast days and at the weekends. This study also provides evidence of an independent effect of atmospheric pollution at high levels.Electronic supplementary materialThe online version of this article (doi:10.1186/s12931-015-0229-z) contains supplementary material, which is available to authorized users.

BackgroundDuring most COPD exacerbations, patients continue to live in the community but there is little information on changes in activity during exacerbations due to the difficulties of obtaining recent, prospective baseline data.MethodsPatients recorded on daily diary cards any worsening in respiratory symptoms, peak expiratory flow (PEF) and the number of steps taken per day measured with a Yamax Digi-walker pedometer. Exacerbations were defined by increased respiratory symptoms and the number of exacerbations experienced in the 12 months preceding the recording of daily step count used to divide patients into frequent (> = 2/year) or infrequent exacerbators.ResultsThe 73 COPD patients (88% male) had a mean (±SD) age 71(±8) years and FEV1 53(±16)% predicted. They recorded pedometer data on a median 198 days (IQR 134–353). At exacerbation onset, symptom count rose by 1.9(±1.3) and PEF fell by 7(±13) l/min. Mean daily step count fell from 4154(±2586) steps/day during a preceding baseline week to 3673(±2258) step/day during the initial 7 days of exacerbation (p = 0.045). Patients with larger falls in activity at exacerbation took longer to recover to stable level (rho = −0.56; p < 0.001). Recovery in daily step count was faster (median 3.5 days) than for exacerbation symptoms (median 11 days; p < 0.001). Recovery in step count was also faster in untreated compared to treated exacerbation (p = 0.030).Daily step count fell faster over time in the 40 frequent exacerbators, by 708 steps/year, compared to 338 steps/year in 33 infrequent exacerbators (p = 0.002).ConclusionsCOPD exacerbations reduced physical activity and frequent exacerbations accelerate decline in activity over time.

Little is known about changes in physical activity during moderate (out-patient managed) exacerbations.6-min walking distance (6MWD) was measured during 50 exacerbations when the patients were stable, and at 3 and 7 days post-exacerbation presentation. At similar time points, quadriceps maximum voluntary contraction (QMVC) was measured during 47 different exacerbations. Physical activity (SenseWear; Bodymedia Inc., Pittsburgh, PA, USA) was recorded over 2 consecutive-week periods post-presentation.6MWD fell from a median 422 m when stable to 373 m on day 3 (p=0.001). Similarly, QMVC fell from 32.6 versus 29.7 kg (p=0.026). Falls in 6MWD were associated with a rise in C-reactive protein (r= -0.364; p=0.041) and increased Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) (r= -0.44; p=0.013). Light physical activity was 2.18 h·day(-1) during the first week post-exacerbation and was less over week 2 (1.98 h·day(-1); p=0.009). Patients who had attended pulmonary rehabilitation had smaller changes in 6MWD than those who had not attended (-35.0 versus -114.9 m; p=0.013). Falls in physical activity were correlated with higher depression scores (rho= -0.51; p=0.006).These findings indicate that exercise capacity and muscle strength fall at exacerbation in chronic obstructive pulmonary disease patients who are treated at home and are free to maintain normal activity.