Patient-reported vision impairment in low luminance predicts multiple falls

Falls occur in more than 170 million people every year, resulting in almost 700,000 annual deaths and are important causes of morbidity and mortality in ageing populations worldwide [1]. Annual fall incidences in older adults further highlight the burden of fall events, ranging between 16 and 29% in Germany [2]. Reducing the number of falls may therefore contribute significantly to reducing the global disease burden in older adults. Visual impairment is a key risk factor for falls, more than doubling fall occurrences, and its prevalence is increasing globally [3, 4]. Besides visual function under daytime conditions, contrast sensitivity, and vision under low luminance, i.e. night-time conditions, have been reported as independent risk factors for falls [5‐10].

Despite several international guidelines recommending an assessment of visual function in individuals at risk of falling [11‐14], visual function testing is not widely performed when evaluating fall risk and is perceived as not feasible by a variety of healthcare providers [15, 16]. The prevalence of visual impairment increases considerably with age, affecting more than 1% of Germans above 60 years [17]. Patient-reports of perceived difficulties with tasks based on vision have been shown to correlate well with objective measures of visual function [18‐20] and require little resources to be recorded. In line with this, various studies confirmed an association between self-reported vision and subsequent falling [8, 21‐27]. While patient-report may provide a more feasible alternative to visual function tests in fall risk assessments, the available studies capture only vision under daylight conditions, whereas the value of assessing patient-reported vision under difficult lighting conditions including night-time has not been investigated in the context of falls prevention. The Vision Impairment in Low Luminance (VILL) questionnaire assesses patient-reported difficulties under low luminance and low contrast conditions and may therefore aid fall risk assessments [28‐30].

Against this background, we assessed the association of patient-reported vision impairment in low luminance, visual function and subsequent falls as well as concerns about falling prospectively in a cohort of older adults.

We included 112 participants (74 women, 66.1%) at a mean age of 70.1 ± 7.0 years (Table 1). Reasons for exclusion from an initial number of 127 participants were missed follow-up in thirteen individuals (reasons: Conflicting schedules, n = 11; death, n = 2) and an incomplete follow-up interview in 2 individuals. The follow-up interval was 584 ± 197 days on average and showed no significant association with reported falling (p = 0.434, Mann Whitney U test). Participants had 1.6 ± 1.2 risk factors of falling on average (Table 2) and varying degrees of visual impairment (VI), with 79.4% with no VI (VA ≤ 0.1 logarithm of the minimal angle of resolution [logMAR], i.e. ≥ 20/25), 18.5% with mild VI (0.2 logMAR ≤ VA ≤ 0.5 logMAR) and 2.1% with moderate or severe VI (VA ≥ 0.25 logMAR) based on best-corrected VA [38]. All participants suffered from ocular diseases, which included retinal diseases (59.8%), glaucoma (24.1%), cataract (30.4%), anterior segment conditions (9.8%) and other eye conditions (24.1%).

Twenty-seven participants recalled falls in the last 12 months, of which 74% led to a medical consultation (Table 2). One participant reported a bone fracture secondary to falling (humerus fracture). The mean number of falls in the eleven participants who reported multiple falls was 2.8 ± 0.8 within a 12-month timeframe. Reported falling and multiple falling were not significantly associated with age, VA or any of the above-mentioned risk factors (p ≥ 0.323 and 0.116, respectively in Mann Whitney U test [age, VA] and Fisher’s exact test [risk factors]). Nonetheless, all analyses were corrected for these factors, since age, VA, and the additional risk factors may confound the association between patient-reported vision impairment in low luminance and reported falls. The mean number of reported falls in the groups that indicated low, moderate, and high concerns to fall were 1.6 ± 1.0 (13 participants), 1.6 ± 0.9 (12 participants) and 3.5 ± 0.7 (2 participants), respectively.

Higher self-reported reading and mobility scores (better vision-related quality of life) were significantly associated with a lower risk of multiple falls at follow-up in an adjusted binary logistic regression analysis (OR = 0.559 and 0.595, p = 0.027 and 0.026, respectively; Table 3; Fig. 1). When looking at multiple falls that led to injuries and consultations in the healthcare system, no significant associations with baseline VILL scores or changes in VILL scores over time were found (p ≥ 0.168 and 0.102 across VILL subscales, respectively). Neither of the VILL subscale scores at baseline were associated with any (minimum 1) falling event at follow-up when compared to no reported falling (p ≥ 0.071 across VILL subscales; Table 3). Worsening in individual VILL scores was not significantly associated with falling or multiple falling in our sample (p ≥ 0.236 across VILL subscales, adjusted for age, VA, risk factors of falling, and the follow-up time interval).

Higher scores of all VILL subscales were significantly associated with lower concerns to fall as measured by the FES-I (p ≤ 0.004, comparing “high concern” to “low concern” categories; Table 4; Fig. 2). Worsening VILL scores over time were not associated with concerns to fall (p ≥ 0.055 across VILL subscales) when adjusting for age, VA, risk factors of falling, and the follow-up interval.

This study found that patient-reported visual impairment concerning reading and mobility tasks under low-luminance and low-contrast conditions using the VILL questionnaire could predict multiple falls in older adults over a 12-month period, when adjusting for age, VA and five established falling risk factors. This further highlights the need for assessing visual function in older adults for the prevention of falls and related complications. Assessments such as the VILL questionnaire are easily implemented in any setting, require very little previous staff training and provide additional valuable information relevant to falls and concerns about falling in the near future but pend further validation of our findings in a larger, geriatric sample.

Our results are well in line with previous studies, where self-reports of vision were significantly associated with falling [8, 21‐27]. While these studies focused on self-assessments of vision under daylight conditions, our study specifically addresses visual difficulties under night-time conditions that occur with normal ageing and in many prevalent age-related eye diseases, such as age-related macular degeneration and glaucoma [39‐41]. Yip and colleagues found a significant association between self-reported vision and falls in a population-based setting when controlling for VA (Odd’s ratio 1.28) [21]. We have also controlled our analyses for participants’ VA and our results support that patient-reported vision domains may be independent risk factors of subsequent falls compared to best-corrected VA alone. Due to the conceptual differences between the VILL and generic self-reports of vision, we are unable to comment on the relationship between these two patient-reports. Niihata et al. investigated visual functioning domains more specifically than other studies and identifed the domains of near vision, visual distress and role limitations due to vision to be significantly associated with falling but did not include any domains on night-time vision in a Japanese cohort [23]. The VILL subscale “reading and accessing information” partially corresponds to the near vision subscale assessed by Niihata et al., and both were significantly associated with falling. However, items from the VILL questionnaire have a focus on low-contrast and low-luminance reading (e.g. “Reading print which is not black”, “Recognizing small objects in dim lighting (e.g. coins)“) rather than vision under day-time conditions [29]. Interestingly, the “emotional well-being” subscale of the VILL questionnaire was not associated with falling in our study, which contrasts the results from the Japanese cohort.

The impact of falls on people’s lives can be devastating since falls are associated with an increased risk of fractures, head injury, depression, hospitalization and death [1, 3, 42, 43]. Thus, prevention of falls is increasingly important in our ageing societies and VI is one of the most relevant risk factors of falling, more than doubling the risk independently of other risk factors [3, 5, 7, 44, 45]. In a nationally representative survey conducted in the United States, more than 25% of visually impaired individuals reported multiple falls over the last 12 months [24]. Our data suggest that self-reported visual difficulties under low-luminance and low-contrast conditions using the VILL reading and mobility subscales may add to the assessment and prediction of risk of falling over and above objective measures of visual function.

Most studies investigating risk factors of falling have measured visual impairment based on VA under high illumination, i.e. daytime conditions. However, multiple population-based studies have reported contrast vision to be significantly associated with multiple falls [5‐8]. A study in 156 community-dwelling older adults found contrast sensitivity and low-contrast visual acuity being even the strongest risk factors of multiple falling besides depth perception [9]. This is in accordance with our finding that a reduction in the reading and mobility subscales of the VILL questionnaire, which focuses on exactly these content domains, are significantly associated with multiple falls. However, our sample was recruited at an eye hospital and despite the majority of participants (79%) not being visually impaired, our approach requires to be further validated in an independent cohort. Interestingly, visual function parameters seem to be unrelated to any of these parameters when looking specifically at a low-vision population [46].

Implementing visual function tests in fall risk assessments is met with numerous challenges. This is particularly relevant for less common vision assessments such as contrast sensitivity or low luminance visual acuity, which become especially important in the context of fall risk assessments in older adults, as such assessments tend to be done by non-ophthalmic healthcare providers. Administration of patient-reported outcome measures (PROMs) on the contrary offers an easily implemented alternative which also yields valuable information related to visual functioning and visual difficulties adding to conventional fall risk assessments. Future studies should also assess the predictive value of assessing self-reported visual impairment in addition to patient-reported difficulties under low illumination.

In addition to reported falls, we also found patient-reported difficulties related to low-luminance and low-contrast vision using the VILL questionnaire to be associated with high concerns in the FES-I, a validated measure of fear of falling and self-efficacy [33‐35]. Fear or falling itself is associated with activity restrictions, frailty, falling and institutionalization [47‐49]. The significant association between the VILL and the FES-I in our dataset further supports the relevance of patient-reported visual difficulties in fall risk assessment. This is supported by the previous literature, where White et al. have identified significant associations between concerns to fall and contrast sensitivity measurements in a cohort of people with age-related macular degeneration [50, 51]. Interestingly, not only the functional (reading and mobility) subscales but also the emotional subscale of the VILL questionnaire were associated with the fear of falling, which may be explained by participants interpreting the concepts “concern” (as assessed by the FES-I) and “worry” (not assessed by the FES-I but related to emotional well-being) in similar ways.

Our study is the first to report an association of patient-reported visual difficulties under challenging light conditions with falls and concerns about falling. Strengths of our study include its prospective design, different outcome measures to support our findings, the comprehensive assessment of additional risk factors for falling and use of a variety of statistical techniques including Rasch models. Nevertheless, our study is limited by its relatively small sample size (11 participants reported multiple falls) and the heterogeneous population included which did not allow us to perform any subgroup analyses with the occurrence of falls as an outcome measure and limits the interpretability of the analyses of multiple falls with injuries, which were reported in less than ten participants. The inclusion criteria of our study were relatively wide and we cannot fully exclude selection bias based on this. Also, since participants were recruited at an eye hospital, selection bias may be present despite 79% of our study participants not being visually impaired. We adjusted our analyses for five recommended risk factors of falling but did not assess several other risk factors commonly associated with falls, including prior history of falling, polypharmacy, and cognitive impairment, or the availability of a caregiver, which may modify the associations. In addition, we had to rely on patient-reports of falls which is limited by memory bias and we did not make use of diaries, medical records or technical devices to objectify falls. We did not perform all follow-up interviews precisely 12 months after the first interview but expect this to have only limited impact on our results since VILL scores did not significantly change over time nor were reported falls associated with the length of the follow-up interval.

Our results indicate that patient-reported visual difficulties under low-luminance and low-contrast conditions are predictive of multiple falls in the future and are associated with concerns to fall. Fall risk assessment may benefit from integrating this easily administered PROM independently of any objective visual function assessments. Future studies should assess how screening for patient-reported visual difficulties can be used to prevent multiple falls in the first place.