Visual impairment at baseline is associated with future poor physical functioning among middle-aged women: The Study of Women’s Health Across the Nation, Michigan Site
Introduction
Visual impairment, defined as visual acuity worse than 20/40 [1], affects 14 million people in the United States and its prevalence increases with advancing age [2]. Visual acuity commonly referred to as clarity of vision, is the ability to distinguish letters and numbers at a given distance. The midlife period, comprising ages 40–65 years, is an important life stage for onset and progression of poor physical functioning and disability [4], [5]. In addition, visual impairment prevalence triples during this life-stage [6].
Disability, which has traditionally been described as a chain of events starting with impairment and leading to limitation before the final onset of disability, affects 47.5 million people in the United States [7], [8]. It is of concern that an increasing trend of disability has been reported among midlife populations, with prevalence estimates ranging from 20 to 40% [5], [8], [9], [10]. Visual impairment is a correlate of disability and poor functioning among elderly populations [11], [12]. Among older adults, visual impairment predicts a greater decline in physical functioning and slower walking speed, thus adversely affecting the quality of life and dependency [13], [14], [15], [16], [17].
Many ophthalmologic conditions including cataract, glaucoma, and age-related macular degeneration that affect both distance and near vision as well as presbyopia that affects near vision are commonly diagnosed during the midlife [18], [19]. Yet studies of the impact of visual impairment on functional decline during midlife are limited. Thus, the objective of this study was to assess the relationship of midlife visual impairment and future physical functioning. We hypothesized that women with poor visual acuity meeting the threshold for visual impairment during midlife would have poorer performance-based physical functioning during the transition to early old age.
Section snippets
Study sample
The Study of Women’s Health Across the Nation (SWAN) is a multi-site, multi-ethnic longitudinal study of the menopausal transition. Michigan is one of seven clinical sites for the study and includes a population-based sample from two Detroit-area communities identified using a community census based on electrical utility listings. Since the study’s inception in 1996, the Michigan site has had a physical functioning protocol. Visual acuity was assessed from 1996 to 2007. The University of
Results
Of the 483 participants, 19.3% had distance vision impairment and 39.5% had near vision impairment. Among the participants with visual impairment for distance vision at baseline, 15.1% had visual acuity of 20/50, 22.6% had 20/70, 10.8% had 20/100 and 7.5% had 20/200 or worse. Among those with visual impairment for near vision at baseline, 19.4% had visual acuity of 20/50, 24.6% had 20/70, 13.1% had 20/100 and 4.7% had 20/200 or worse. Characteristics of the study population at the time of
Discussion
The findings of this study show that, among midlife women, visual impairment is a marker of poor physical functioning up to 10 years later. Women with distance visual impairment had 4.26 s or 19% longer stair climb time and 2.81 cm or 6% shorter forward reach distances than women without distance visual impairment, confirming our hypothesis. Additionally, women with near vision impairment had 2.26 cm or 6.25% shorter forward reach distances. The magnitude of difference in forward reach is similar
Contributors
N.C. conducted the statistical analysis, participated in the interpretation of data, and drafted the article.
S.H. contributed to the conception and design of the study, interpretation of data, and review of the article.
S.M. contributed to interpretation of data and review of the article.
D.M. contributed to interpretation of data and review of the article.
Q.P. contributed to the analysis and interpretation of data and review of the article
C.K.-G. contributed to the conception and design of the
Funding
The Study of Women’s Health Across the Nation (SWAN) has grant support from the National Institutes of Health (NIH), DHHS, through the National Institute on Aging (NIA), the National Institute of Nursing Research (NINR) and the NIH Office of Research on Women’s Health (ORWH) (Grants U01NR004061; U01AG012505, U01AG012535, U01AG012531, U01AG012539, U01AG012546, U01AG012553, U01AG012554, U01AG012495). The content of this manuscript is solely the responsibility of the authors and does not
Ethical approval
The University of Michigan Institutional Review Board approved the study protocol and written informed consent was obtained from each participant at each study visit. This study conformed to the principles of the Declaration of Helsinki.
Conflict of interest
The authors declare that they have no conflict of interest.
Provenance and peer review
This article has undergone peer review.
Acknowledgement
We thank the study staff at each site and all the women who participated in SWAN.
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