Elsevier

Preventive Medicine

Volume 95, February 2017, Pages 103-109
Preventive Medicine

Changes in physical activity, sedentary time, and risk of falling: The Women's Health Initiative Observational Study

https://doi.org/10.1016/j.ypmed.2016.11.025Get rights and content

Highlights

  • Increasing physical activity (PA) may be associated with a greater risk of falling among postmenopausal women.

  • Increasing sedentary time may slightly decrease risk of falling among postmenopausal women.

  • Falls risk must be weighed against PA benefits for prevention of chronic diseases among postmenopausal women.

  • Further research is needed to improve safety and support continued PA with aging among postmenopausal women.

Abstract

Falling significantly affects quality of life, morbidity, and mortality among older adults. We sought to evaluate the prospective association between sedentary time, physical activity, and falling among post-menopausal women aged 50–79 years recruited to the Women's Health Initiative Observational Study between 1993 and 1998 from 40 clinical centers across the United States. Baseline (B) and change in each of the following were evaluated at year 3 (Y3) and year 6 (Y6; baseline n = 93,676; Y3 n = 76,598; Y6 n = 75,428): recreational physical activity (MET-h/wk), sitting, sleeping (min/day), and lean body mass by dual energy X-ray absorptiometry (subset N = 6475). Falls per year (0, 1, 2, ≥ 3) were assessed annually by self-report questionnaire and then dichotomized as ≤ 1 and ≥ 2 falls/year. Logistic regression models were adjusted for demographics, body mass index, fall history, tobacco and alcohol use, medical conditions, and medications. Higher baseline activity was associated with greater risk of falling at Y6 (18%; p for trend < 0.0001). Increasing sedentary time minimally decreased falling (1% Y3; 2% Y6; p < 0.05). Increasing activity up to ≥ 9 MET-h/wk. (OR: 1.12, 95% CI: 1.03–1.22) or maintaining ≥ 9 MET-h/wk. (OR: 1.20, 95% CI: 1.13–1.29) increased falling at Y3 and Y6 (p for trend < 0.001). Adding lean body mass to the models attenuated these relationships. Physically active lifestyles increased falling among post-menopausal women. Additional fall prevention strategies, such as balance and resistance training, should be evaluated to assist post-menopausal women in reaching or maintaining levels of aerobic activity known to prevent and manage several chronic diseases.

Introduction

The propensity to fall increases with aging, often due to other age related issues, such as impaired vision, balance, and mental acuity (Rubenstein, 2006). Although many falls result in minor injuries, approximately 10% will result in fractures which are associated with significant morbidity and mortality in the aged (Gillespie et al., 2012). Reductions in falls among community dwelling older adults engaging exercise interventions offers hope (Gillespie et al., 2012), as does the protection against fracture with higher baseline physical activity demonstrated in the Women's Health Initiative (WHI) (Robbins et al., 2007), but overall, the association between physical activity and falls in the literature has been inconsistent (Clarke et al., 2015). Physical activity patterns over time may prove to be more predictive of falls than exercise interventions or assessment of physical activity at a single time point. Longitudinal changes in physical activity and body composition, which may mediate the falls benefit of physical activity through preservation of muscle mass (LaStayo et al., 2003), are needed to better understand their independent and joint roles in falls risk. However, because prospective studies on older adults typically do not have repeated prospective measures on these factors, they have yet to be fully explored with respect to incidence of falling.

In the United States, physical activity decreases dramatically in adulthood, stabilizing at relatively low levels in middle aged women (Caspersen et al., 2000). Low levels of physical activity have been associated with decreased muscle mass (Morley et al., 2001). Meanwhile, sedentary time, distinctly different than insufficient moderate to vigorous physical activity (Owen et al., 2010), increases with aging (Clark et al., 2010). High sedentary time may also aid in skeletal muscle decline and has been shown to be a risk factor for falling in studies with 1–2 years follow-up (Thibaud et al., 2012).

We sought to determine whether prospectively assessed physical activity patterns, including sedentary time, are associated with the risk of falling over several years and whether risk of falling is mediated by body composition. We hypothesized that decreasing physical activity over time would be associated with increased risk of falling among postmenopausal women (Fig. 1). High sedentary time was also hypothesized to increase risk of falling.

Section snippets

Study population

The WHI Study recruited postmenopausal women aged 50–79 years at 40 WHI clinical centers across the United States between 1993 and 1998 to four clinical trials and an observational study (Design of the Women's Health Initiative Clinical Trial and Observational Study, 1998, Hays et al., 2003). Only women enrolled in the observational study were included in this analysis (N = 93,676); body composition was measured in those enrolled at the Pittsburgh, PA; Birmingham, AL; and Tucson-Phoenix, AZ sites (

Results

Overall, the mean physical activity level for the cohort was 13.7 (± 14.4) MET-h/wk. at baseline, 13.6 (± 14.6) MET-h/wk. at year 3, and 13.1 (± 14.2) MET-h/wk. at year 6. The change in physical activity across the cohort was − 0.4 (± 12.4) MET-h/wk. from baseline to year 3 and − 0.9 (± 13.5) MET-h/wk. from baseline to year 6. Total sedentary time (h/day spent sitting or sleeping) was 15.0 (± 4.2) h/day at baseline, 14.7 (± 3.7) h/day at year 3 and 14.7(± 3.8) h/day at year 6. Inactive time was reduced by − 

Discussion

Contrary to our hypothesis, we found that active lifestyles and increases in physical activity over time were associated with increased fall risks among postmenopausal women aged 50–79 at baseline. Although reduction in falls has been supported by several exercise interventions (Gillespie et al., 2012), the positive studies tended to include multifactorial interventions (i.e. combination of physical activity, balance training, home hazards assessment, medication assessment, technical aids,

Conclusion

Physically active lifestyles increased falling among post-menopausal women. Additional fall prevention strategies, such as balance and resistance training, should be evaluated to assist post-menopausal women in reaching or maintaining the level of aerobic activity known to prevent and manage several chronic diseases.

Disclosure statement

The authors have declared no conflicts of interest.

Funding

This work was supported by the National Cancer Institute (CA023074); and the WHI program which is funded by the National Heart, Lung, and Blood Institute, National Institutes of Health, and the U.S. Department of Health and Human Services (HHSN268201100046C, HHSN268201100001C, HHSN268201100002C, HHSN268201100003C, HHSN268201100004C, and HHSN271201100004C).

Short list of WHI investigators

Program office: National Heart, Lung, and Blood Institute, Bethesda, Maryland.

Jacques Rossouw, Shari Ludlam, Dale Burwen, Joan McGowan, Leslie Ford, and Nancy Geller.

Clinical coordinating center (Fred Hutchinson Cancer Research Center, Seattle, WA): Garnet Anderson, Ross Prentice, Andrea LaCroix, and Charles Kooperberg.

Investigators and academic centers: (Brigham and Women's Hospital, Harvard Medical School, Boston, MA) JoAnn E. Manson; (MedStar Health Research Institute/Howard University,

Transparency document

Transparency document.

Acknowledgements

We are thankful for the contribution of the WHI investigators and staff at the clinical centers, clinical coordinating center, and project office.

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