Maintaining physical activity among older adults: 24-month outcomes of the Keep Active Minnesota randomized controlled trial☆
Introduction
Substantial evidence documents the health benefits of regular physical activity (PA) (Physical Activity Guidelines Advisory Committee, 2008). Many of the beneficial effects of PA are particularly salient for mid-life and older adult populations (Angevaren et al., 2008, Blair et al., 1992, Brach et al., 2004, Colbert et al., 2004, Cox et al., 2004, Elavsky et al., 2005, Feskanich et al., 2002, Hughes et al., 2004, King et al., 2008, Liu-Ambrose et al., 2008, Lord et al., 1995, Mayer-Davis et al., 1998, McAuley et al., 2006, Pescatello et al., 2004, Tuomilehto et al., 2001, Vallance et al., 2007, Weuve et al., 2004). Unfortunately, mid-life and older adults in the U.S. remain relatively sedentary. The 2007 Behavioral Risk Factor Surveillance System (BRFSS) documents that, more than half of adults age 45–54 years (52%) were obtaining less than recommended levels of PA, with the same being true for 53% of adults age 55–64 years and for 61% of adults ages 65 and over (Centers for Disease Control and Prevention, 2007). To increase US population PA levels, health plans and public health policy makers are seeking low-cost intervention strategies that produce long-term behavior changes and have potential to reach a broad spectrum of the population.
Complementary routes to reach national PA goals include increasing the number of sedentary individuals who initiate PA and increasing the long-term maintenance of beneficial levels of PA. This is underscored by evidence from a number of PA intervention programs targeted to mid-life and older adults that sustaining recommended PA levels is difficult for this population. Attrition rates in the first year of such studies range from about 27% to 50% (Jacobsen et al., 2003, Jancey et al., 2007, Prohaska et al., 2000, Schmidt et al., 2000, Tu et al., 2004) with the most rapid attrition typically occurring within the first three months (Jancey et al., 2007, Schmidt et al., 2000, Tu et al., 2004). These data, coupled with the observation that prevalence of sedentary behavior increases with age, (Centers for Disease Control and Prevention, 2005) suggest that population levels of PA may be substantially increased by preventing the currently active, particularly those with recently increased PA levels, from becoming sedentary.
The optimal intervention delivery method is also an important question. The efficacy of clinic-based approaches to increasing PA is equivocal (Bull et al., 1999, Eaton and Menard, 1998, Goldstein et al., 1999, The Writing Group for the Activity Counseling Trial Research, G., 2001, Walsh et al., 1999). More recent studies linking brief primary care based advice/counseling with referrals to telephone-based counseling are more promising (Anderson et al., 2005b, Anderson et al., 2005, Harrison et al., 2005, Kerse et al., 2005, Pinto et al., 2005a, Pinto et al., 2005b, van Sluijs et al., 2005). However, such approaches are relatively expensive, difficult to implement in busy practice settings, and have variable reach to community populations. A recent literature review documents that home- and group-based interventions can increase PA in the short-term, suggesting that community based interventions may be viable alternatives to clinic-based approaches and have greater potential for broad population reach (Van der Bij et al., 2002).
We designed the Keep Active Minnesota (KAM) project to evaluate the efficacy of a population-based approach to promoting PA maintenance among currently active mid-life and older adults who reported an increase in PA within the past year. Participants were randomized to an interactive telephone and mail-based PA support program (KAM) or usual care (UC) and followed for a two year period. This report presents the results of the a priori study hypotheses: Hypothesis 1 KAM intervention participants will maintain higher absolute estimated kcal energy expenditure from baseline to 6, 12, and 24 months relative to the kcal expenditure observed among the UC group. Hypothesis 2 PA maintenance, defined as kcal expenditure at 6, 12, and 24 months relative to one's baseline expenditure, will be higher among KAM participants than among the UC group.
Section snippets
Target population
The study was conducted among 50–70 year old members of the HealthPartners health plan in the Minneapolis/St. Paul metropolitan area.
Eligibility, sampling, and recruitment
We have discussed eligibility, sampling and recruitment in detail elsewhere (Martinson et al., 2008). Briefly, we used health plan administrative data to identify age-eligible members who had been enrolled in the health plan for at least 11 of the 12 months prior to eligibility screening. Recruitment was initiated through direct mailings to random samples of
Sample characteristics
With respect to age and race/ethnicity, those enrolled in the trial were reasonably representative of the recruitment pool of age-eligible health plan members; themselves reflective of the local community.(Martinson et al., 2010) Baseline demographic characteristics of participants are shown in Table 2. Our target population being individuals reporting increased MVPA within the past year to a minimum of 30 min on at least 2 days/week, it is not surprising that one-third reported participation in
Discussion
This relatively low-intensity telephone and mail-based PA maintenance intervention is one of the first studies to focus on maintenance of PA levels among adults ages 50 to 70 years who had recently increased their PA. Compared to UC subjects, those receiving the KAM intervention had significantly higher mean energy expenditures at 6, 12, and 24 months after randomization. The magnitude of the difference in PA between groups, roughly an additional 200 kcal/wk in the KAM group, was statistically
Human participation protection
This study was reviewed and approved by Regions Hospital Institutional Review Board.
Conflict of interest statement
The authors declare that there are no conflicts of interest.
Acknowledgments
This study was supported by a grant from the National Institute on Aging (R01 AG023410). The project was initiated and analyzed by the study investigators. At no point was the study sponsor involved in the study design; in the collection, analysis or interpretation of the data, in the writing of this report; or in the decision to submit the paper for publication. For her capable project management during the study startup period we thank Kirsten Hase. For their dedicated service as a Data
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Clinical Trial Registration Number at ClinicalTrials.gov: NCT00283452.