In a longitudinal study of changes in physical activity and FoF levels in persons with varying degrees of visual impairment, we found a long-lasting impact of falls on mobility (both physical activity and FoF) after injurious falls, but not after non-injurious falls. Specifically, first-year injurious falls were associated with a significant decline in physical activity over the three-year study period, but not with changes in FoF. However, non-injurious falls were not associated with a drop in physical activity nor a worsening of FoF over the full study period, nor were such changes observed in non-fallers. Our findings indicate that among persons with visual impairment from glaucoma, injurious fallers lower their daily activity over time but do not demonstrate higher levels of FoF compared to their counterparts who do not fall.
Our results add to the published literature examining whether falls, or injuries occurring with falls, are associated with restriction of physical activity [4, 10]. A cross-sectional study from the Baltimore Longitudinal Study of Aging (BLSA) did not find associations between self-reported falls in the last year and accelerometer-defined physical activity [4]. However, the impact of fall status on the within-individual change in activity over time was not evaluated. Also, the retrospective assessment of falls via questionnaire is subject to substantial recall bias, i.e., those who recall their falls are more likely to sustain injuries, while less intense falls may be forgotten [46]. A three-year longitudinal study did find that injurious falls were associated with lower physical activity levels; however, physical activity was obtained by self-report, which typically shows very poor correlations with objective measures of physical activity [20–22], and is less reflective of important biological parameters such as BMI, diabetes and hypertension [47]. As such, our longitudinal study, which captured falls prospectively through monthly mail in calendars, and examined physical activity objectively over four annual visits, provides greater accuracy and is less subject to bias than prior studies. In the BLSA, investigators have demonstrated an average drop of 1.3% per year in overall activity from mid-to-late life [20], similar to our non-faller and non-injurious faller groups, but less than the decline observed in our injurious fallers (roughly 7% fewer steps and 7% fewer active minutes per year).
Our study also examined whether fall status was associated with changes in FoF over time. Previous research has demonstrated that any falls reported within the last 3 or 12 months were associated with a higher likelihood of FoF, as judged by the individual’s response to the question “do you ever limit activities because you are afraid of falling?” 24 or “have you been worried or afraid that you might fall?” [48] The use of a single question to evaluate FoF will have less precision for measuring within-person changes in FoF as compared to the current approach which uses a reliable and valid questionnaire that enables quantifying FoF levels and changes in levels resulting from falls. Our study demonstrated that first-year injurious fallers had significant worsening of FoF over the three year study period; however, worsening of FoF at a rate just short of statistical significance was also observed in the non-faller and non-injurious faller groups, and the rate of FoF changes over time were not significantly different between those with injurious falls, non-injurious falls, or no falls over the first study year. Thus, it is not clear that fall-related injuries, when evaluated over a single study year, have a clear influence on the longitudinal trajectory of FoF, though it remains possible that severe injuries and/or repeated falls may impact FoF over time.
Our findings strongly suggest that injurious falls have significant consequences versus those experiencing a fall that is non-injurious. Injurious falls in this study were associated with reductions in physical activity over the three-year study period. Specifically, an individual who had one or more injurious falls in the first year reduced their walking over the three-year study period by an average of 350 steps/year, and demonstrated average 11 fewer daily active minutes per year. An observational study of 8188 healthy women aged 70–75 in Australia reported that lower physical activity was associated with an increased risk of fall-related bone fracture [11]; our findings emphasize these relationships could be reciprocal, with fall-related injuries also resulting in less physical activity. Of note, the present study suggests that fall-related injuries may contribute to functional decline over a long period extending well past the fall occurrence (up to 3 years).
The magnitude of activity change (average of 350 steps/year and 11 active minutes/year over the three-year study period) in injurious falls is significant given that previous studies report that 30 fewer daily minutes of walking is associated with a 23% higher risk of coronary heart disease [49], and fewer steps per day is significantly associated with higher all-cause mortality (hazard ratio = 2.04 for 4000 steps/day vs. 8000 steps/day) [50]. We also observed an average of 1.5 fewer minutes of MVPA/day (roughly 10 fewer weekly minutes) each year for injurious fallers, which is substantial given that World Health Organization (WHO) recommends older adults should conduct at least 150 minutes of moderate-intensity physical activity a week to maintain functional capability and overall well-being [51]. Our data add compelling evidence about the impact of substantial mobility declines associated with injurious falls on longevity and well-being, which supports the need for interventions to prevent injurious falls and rehabilitation programs to enhance the recovery from any detrimental effects of falls, particularly with regards to safely resuming/increasing physical activity [52, 53].
Our study has several limitations. First, study participants were recruited from one study site and had varying degrees of glaucoma; therefore our results may not be generalizable to all visually impaired older people, or patients without visual impairments. As such, it remains unclear whether any fall occurrences with respect to other illnesses (other than visual damage) also influence the longitudinal change of physical activity and FoF in the same manner. Additionally, other factors (e.g., home hazard modification) [52] might confound the association between falls status and activity in observational studies, though such factors would only affect results if they were differential across fall status. Moreover, such changes, if protective, would tend to bias our results towards the null. Finally, it was our original hypothesis (set forth in our grant) that first-year fall events would have implications for physical activity and fear of falling over the full 3 year study period (declines were still expressed as change per year, given that complete follow-up was not present in all participants). However, it is quite possible, perhaps even likely, that the impact of injurious falls varied over time. Indeed, it might appear from Fig. 1A that injurious falls caused physical activity to decline in the year of the fall, with these declines sustained in later years, while non-injurious falls created a decline that was temporary. We did not formally test the significance of these trends noted post-hoc, though they should be evaluated in future studies.
In summary, our study found that in glaucoma patients, injurious falls contributed to a substantial change in physical activity over the three-year study period, although FoF levels remained unchanged. However, non-injurious falls were associated with neither a drop in physical activity over the full study period nor worsening of FoF. Further work is needed to identify effective interventions to prevent injurious falls and evaluate rehabilitation programs to improve physical and mental recovery from falls, particularly those resulting in injury.
Declarations