Close-Up on Our Newest Paper: Accelerometer Cut Point Methods for Midlife Women with Cardiovascular Risk Markers

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Our research team takes a specific interest in women who are between the ages of 40 and 60, a period often called “midlife.” Women in this age range have elevated age-related risk for cardiovascular disease (CVD), are beginning menopause, and are experiencing health conditions such as type 2 diabetes and high cholesterol – all of which independently increase CVD risk. Therefore, midlife women have a lot to gain from physical activity, as it can protect against CVD even when other risk factors are present. So health professionals have spent a good bit of effort on promoting physical activity in this group. A focus has been on getting women to meet U.S. Department of Health and Human Services recommendations for moderate-to-vigorous physical activity (MVPA), or activity at an intensity that gets the heart rate up.

If you’re someone who tries to follow public health recommendations for physical activity (or you do research in the area of physical activity), you may be aware that recommendations changed last year. Specifically, the U.S. Department of Health and Human Services changed the way it defines MVPA. For several years prior to 2019, guidelines indicated that MVPA should happen in “bouts” (or episodes) sustained for at least 10 minutes at a time, and that adults should get 150 minutes of this kind of activity per week. The most recent report has removed the requirement that MVPA happen in 10-minute bouts, indicating that all MVPA is helpful for accruing health benefits. Although this is good news, as it means that shorter bouts of MVPA now count toward the 150-minute total, it raises important questions about population-level activity engagement. For example, most U.S. adults fail to meet the old guidelines; is that true now that shorter bouts count?

To make matters even more complicated, measurement of physical activity engagement isn’t entirely consistent across research studies. There are several methods for calculating whether activity reaches the threshold to be considered MVPA, and it’s not clear whether these methods give the same answers about how much time midlife women spend in MVPA. In other populations (such as among children and pregnant women), different methods give wildly different answers about how much MVPA participants get – differences of up to 100 minutes.

In our new publication (currently in press at Menopause), we took a closer look at two questions about midlife women’s MVPA:

(1)  How different are estimates of MVPA between considering only 10-minute bouts and considering all minutes?

(2)  How different are estimates of MVPA (bouted and all minutes) between different calculation methods?

What did we do?

We looked at four popular calculation (or “cut point”) methods for MVPA: Freedson et al. (1998), Swartz et al. (2000), Matthews et al. (2008), and Troiano et al. (2008) in two separate studies. The first was an observation-only study conducted by our CHASE team at The University of Scranton (before we moved to Rowan University in 2018), and the second was part of a weight loss clinical trial conducted by our collaborators at Drexel University’s WELL Center. This two-study approach allowed us to replicate our initial findings in a separate sample and confirm that findings were consistent across contexts.

What did we find?

In both studies, we met with midlife women at our research center for brief interviews, to train them in the use of a research-grade physical activity monitor to wear during waking hours for the following 7 days. Both studies showed that (1) using non-bouted (total) minutes of MVPA resulted in significantly more minutes than using 10-minute bouts only (across calculation methods), and (2) calculation methods meaningfully differed in the number of MVPA minutes they estimated (across non-bouted and bouted MVPA). Additionally, two of the methods (Freedson et al., and Troiano et al.) showed that midlife women did not meet MVPA recommendations using either bouts or not-bouts, while the other two methods (Matthews et al., and Swartz et al.) showed that midlife women met or exceeded MVPA recommendations if non-bouted minutes were considered.

What does this tell us?

Overall, our series of studies seems to be the first of its kind to focus on differences between cut point methods for physical activity among midlife women with elevated CVD risk, and to compare MVPA bouts with total (non-bouted) minutes. Findings suggested that using different cut points provide different answers, and researchers should keep in mind respective strengths and weaknesses of each method. This work is not only timely considering recent changes in physical activity recommendations, but also necessary for understanding how to estimate MVPA toward the goal of reducing CVD risk in midlife women.

What was it like to work on this study?

“It is amazing to think about how far the lab has come with various iterations of this [observational] study. When it first started, Dr. Arigo and I were at The University of Scranton running a pilot for our WHADE project, which is now in its full form. At this time, we were just beginning to learn the ins and outs of recruiting through primary care. I still remember being excited at the thought of getting any experience in this setting. This was my first research experience recruiting outside of the college population. It was thrilling to be recruiting those out in the community, trying to meet people where they were. ”

– Kristen Pasko, CHASE Lab Member

“Collaborating with Dr. Arigo and her team at Rowan University was an incredible experience. I processed some of the accelerometers from Drexel University that were used as part of this larger study. Working on this project allowed me to see the research process through from start to finish, from assisting with analyzing the raw data to the writing of the manuscript. Before this project, I had never worked on research specifically relevant to the question of women’s health and physical activity. It was a pleasure to work with Dr. Arigo and her students to answer such an important research question that has clear clinical implications for how women are advised to engage in physical activity.”

–  Savannah Roberts, Former research coordinator at Drexel’s WELL Center (current Ph.D. student at the University of Pittsburgh)

“This was a pretty large project that involved a number of team members, for two different studies, across three different universities (including Rowan, Drexel, and Penn State). So it took a lot of open communication and teamwork to bring the project together and communicate what we found. Our group was fantastic and stayed focused on learning what we could from the project. It’s been fun and rewarding to do this work and see it published in a journal that focuses on women’s health.”

– Dr. Dani Arigo, CHASE Lab director

Next Steps

If you follow our posts, you’ll remember that recently, we summarized our review of studies that assess social comparison using within-person methods – those that capture comparisons repeatedly for the same person over days or weeks. This review and the physical activity study described in this post was designed to help us make informed decisions about how to estimate midlife women’s physical activity in our women’s health study, which is running now. The goal of this work is to understand the circumstances that contribute to changes in midlife women’s physical activity from day to day, and ultimately, to design better activity interventions for midlife women. Stay tuned as we work toward these goals!

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