Last week, a group of UK based researchers reported the results of a study that found notable differences in COPD patient physical activity achieved during pulmonary rehabilitation depending on what season of the year patients started their rehab. (Sewell L, et al. Seasonal Variations Affect Physical Activity and Pulmonary Rehabilitation Outcomes. J Cardiopulm Rehabil Prev. 2010 Jun 14. [Epub ahead of print])
The study findings shed light on a number of interesting differences in COPD patient conditioning and performance based on when patients start rehab (spring, summer, autumn or winter). The most noteworthy finding according to the study authors was that COPD patients who began a pulmonary rehab program during the winter months achieved the largest boost in subsequent physical activity – a 130% increase in mean “physical activity” compared to baseline measures taken prior to the rehab program (the term “physical activity” in this study means how much COPD patients move around doing normal every day activities outside of the pulmonary rehabilitation program – sometimes referred to as “activities of daily living” by respiratory care professionals).
The pulmonary rehab program followed during the study lasted 7 weeks and involved 95 patients. COPD patients visited an outpatient rehab facility 2 times each week for 2 hours. In each session, patients participated in 1 hour of aerobic and strength training exercise and 1 hour of educational counseling on topics ranging from nutrition to breathing techniques to proper use of medications among other topics. Patients were also asked to exercise at home on a daily basis by walking and practicing some of the strength training exercises. Patients kept a log of their unsupervised at-home exercise and provided their data to the research team.
The fact that COPD patients who began rehab during the winter months saw the largest increase in physical activity did not surprise the researchers given that in geographic areas that experience cold winters (such as the UK), the incidences of COPD exacerbations that require hospitalization jump significantly. The reigning belief is that when COPD patients are exposed to cold, inhospitable outdoor/indoor temperatures they become far more sedentary. The more sedentary a COPD patient is, the lower their level of physical conditioning.
By way of example, patients in the study who began rehab in the summer months averaged almost 9,000 activity units on the device used to measure physical activity (a uniaxial accelerometer – sort of a souped-up pedometer), while patients who began in the winter months averaged just over 3,000 activity units. That’s obviously a huge difference and drives home the researchers point.
What seemed to surprise the researchers is how little the rehab program lifted the summer group’s physical activity (2% increase) in comparison to the winter group (130% increase – which translated to over 7,000 activity units for the winter group by the end of the study – still below the summer group but much closer).
Does this mean that pulmonary rehab is not effective for those who commence a program in the summer months? Absolutely not. It just means that COPD patients who begin a rehab program during milder/warmer/dryer weather are more active at the outset of a rehab program compared to those who begin in the winter months and therefore don’t achieve as dramatic gains in their activity levels outside of rehab.
In support of this contention it is worthwhile to look at the improvement in exercise performance of the four seasonal groups reported in this study. To assess exercise performance, the researchers used a test known as the Incremental Shuttle Walk Test (ISWT). In an ISWT patients are asked to walk as fast as they reasonably can for as long as they reasonably can before fatigue requires them to stop. The researchers asked patients to perform 2 ISWT tests, one at the outset of the program (baseline) and one at the end of the study.
Not surprisingly, the winter group had the lowest mean baseline ISWT at 146 meters walked before fatigue required them to stop, while the summer group had the highest mean baseline ISWT at 225 meters. Both groups (in fact, all four groups) saw their end-of-study ISWT mean distance walked rise between 79-83 meters. This translated into a 54% improvement in exercise performance for the winter group and a 37% improvement in the summer group with the spring and autumn groups’ improvement falling between these two extremes.
While the researchers concluded there was not a statistically significant difference in the absolute increase in distance walked among the four seasonal groups, it seems clear to us that all four groups experienced statistically significant improvements in overall exercise performance regardless of seasonality.
So while seasonality does play a role in COPD patient physical conditioning at the outset of a pulmonary rehab program, and as a result can influence the degree of improvement experienced in rehab, all COPD patients can experience significant conditioning benefits by participating in such a program regardless of season.
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