Gender differences in four-year incidence of self-reported and performance-based functional disability: The International Mobility in Aging Study

Highlights

• Women had a higher adjusted incidence of ADL and mobility disability over time.

• Women have higher incidences of disability in self-reported outcomes measures, but not not necessarly in performance-based measures.

• Future research should focus on exploring sources of discrepant self-reporting of incident disability between men and women.

Abstract

Objectives

To examine differences in incidence of functional disability between older women and men.

Methods

2002 participants (65–74 years) were recruited in 2012 from Canada, Brazil, Colombia, and Albania, and re-assessed in 2016. Three measures of functional disability were used (1) Difficulty in any of five mobility-related Activities of Daily Living (ADL disability); (2) Self-reported difficulty climbing a flight of stairs or walking 400 m (mobility disability); and (3) Poor physical performance. We estimated the adjusted gender-specific incidence risk ratios (IRR) for each outcome in 2016.

Results

In 2016, 1506 participants (52% women) were re-examined, 80% of the surviving cohort. Among those not disabled in 2012, seventy-four (12.9%) men developed ADL disability, while 105 (19.2%) developed mobility disability, and 97 (16.1%) developed poor physical performance. For women, numbers were higher 120 (21.4%) developed ADL disability, 117 (26.5%) developed mobility disability, and 140 (23.0%) developed poor physical performance. Compared to men, women had a higher adjusted incidence of self-reported ADL disability (IRR 1.4; 95% CI 1.04–1.88) and mobility disability (IRR 1.4; 95% CI 1.06–1.77), but not of poor physical performance (IRR 1.03; 95% CI 0.88–1.32).

Conclusions

Although women have a higher self-reported incidence of ADL and mobility disability than men, there was no significant difference in poor physical performance. Reasons for this discrepancy between self-reported and performance-based measures require further investigation. Understanding gender differences in functional disabilities can provide the basis for interventions to prevent mobility loss and minimize any gender gap.

Introduction

Maintaining the ability to move and function independently into older age is central to ongoing involvement in communities, health, and well-being, and poses a major challenge as populations age. Up to one half of adults 65 or older in North America report functional disabilities that affect their mobility, social participation, and quality of life (Webber, Porter, & Menec, 2010). Functional disabilities such as mobility limitations are a precursor of more than half of end-stage disabilities in older adults. Typically, functional disabilities are measured using self-reported outcome measures (e.g. Lower Extremity Functional Scale (Binkley, Stratford, Lott, & Riddle, 1999)) or performance-based measures (e.g. Short Physical Performance Battery (da Camara, Alvarado, Guralnik, Guerra, & Maciel, 2013), and these measurement approaches complement each other and allow for better capturing differences in function (Nielsen et al., 2016; Rodrigues, Facchini, Thume, & Maia, 2009). These disabilities are also associated with gender, since there are differences in proportions of older women and men with disabilities (Fried, Bandeen-Roche, Chaves, & Johnson, 2000).

Although women have longer life expectancies than men, they report greater disability at each age (Mechakra-Tahiri, Freeman, Haddad, Samson, & Zunzunegui, 2012). Gender differences in the prevalence of functional disabilities (e.g. mobility limitations) have been observed consistently in cross-sectional studies worldwide (Leveille, Resnick, & Balfour, 2000; Murtagh & Hubert, 2004), despite that the magnitude of these differences varies widely from place to place. For instance, an analysis of the World Health Survey, a large international database, found gender variations in mobility disability across 70 countries (Mechakra-Tahiri et al., 2012). While the difference between men and women was greatest in the Eastern Mediterranean region and smallest in the Western Pacific region, differences were evident in all WHO defined regions (Mechakra-Tahiri et al., 2012). Longitudinal studies have also detected a gender gap in prevalence of functional disability and, sometimes, in the incidence of disability. For example, the Established Populations for Epidemiologic Studies of the Elderly (EPESE), a large multisite longitudinal study of aging in four U.S. states and one of the first to investigate gender gaps in mobility found a higher incidence of mobility disability in women after 4 years of follow–up (Leveille, Penninx, Melzer, Izmirlian, & Guralnik, 2000).

Despite extensive study of gender differences in functional disability, the existing body of research has limitations. First, while cross-sectional population studies typically find that compared to men, women report worse physical functioning (with one exception (Louie & Ward, 2010)), studying the gap between women and men in incidences of functional disability does not seem to yield consistent findings (Rodrigues et al., 2009). Authors of a systematic review identified conflicting evidence in longitudinal studies about the gap in incident disability (Rodrigues et al., 2009), which they attributed to frequent failure to adjust for important confounders (e.g. education, cognitive state). They noted that once confounders were taken into account, the incidence of functional disability was similar for women and men (Rodrigues et al., 2009). This review included mainly studies from high-income countries and sometimes persons less than 65 years old; furthermore, the review authors’ conclusion was based only on a subjective analysis of included studies. A second limitation of the existing literature is that very few studies have used both self-reported and performance-based outcomes to study gender gaps in disability, despite recognized divergence in these measures (Rodrigues et al., 2009). Finally, the majority of relevant studies to date have been conducted in the United States; only a small body of work on gender and disability has included participants from low- and middle-income countries where there greater lifetime social and economic inequality precipitates greater health discrepancies (Onadja, Atchessi, Soura, Rossier, & Zunzunegui, 2013). The few studies that included participants from low- or middle-income countries were all cross-sectional (studying prevalence of disability not incidence rates) (Khadr & Yount, 2012; Merrill, Seeman, Kasl, & Berkman, 1997; Rahman & Liu, 2000; Yount & Agree, 2005; Zeki Al Hazzouri, Mehio Sibai, Chaaya, Mahfoud, & Yount, 2011; Zunzunegui et al., 2015).

The main objective of this study was to examine gender differences in incidence of functional disability in older adults from five sites in four countries using both self-reported and performance-based measures. We hypothesised that we will find a higher incidence of functional disability among women compared to men in both self-reported and performance-based measures over the study period.