What Is a Falls Risk Factor? Factors Associated with Falls per Time or per Step in Individuals with Glaucoma

Abstract

Objectives: To determine whether visual field (VF) damage or other factors confer a similar risk of falling when falls are ascertained as a rate over time (falls/year) as when ascertained over activity (falls/step).

Design: Prospective, observational cohort study.

Setting: Clinic-based recruitment with real-world monitoring of falls and physical activity.

Particpants: Individuals with glaucoma or suspected glaucoma (N=230).

Measurements: Participants recorded falls using daily calendars, with injuries identified in a follow-up questionnaire. Annual 1-week accelerometer trials were used to estimate steps. VF results from both eyes were merged to determine integrated VF sensitivity, with lower sensitivity indicating greater VF damage. Other potential risk factors for falls (age, sex, race, comorbid illness, polypharmacy) were determined using questionnaires.

Results: The cumulative probability of falls was 45.2% at 12 months and 61.6% at 24 months; cumulative probability of injurious falls was 23.3% at 12 months and 40.0% at 24 months. Greater VF damage was associated with higher rates of falls/steps (incident rate ratio = 1.40/5 dB decrement in sensitivity; p = .004) but not with more falls/year (incident rate ratio = 1.25/5 dB decrement in sensitivity; p = .07). Several additional variables (older age, female sex, more comorbid disease) were also associated with a higher rate of falls/step (p < .02 for all) but not with falls/year (p > 0.10). Black participants had fewer falls/year than whites (p = .002) but did not differ in falls/step (p = .07). Similar results were obtained when injurious falls were analyzed.

Conclusions: Risk factors associated with frequent falls when walking (falls/step) are not properly identified when analyzing falls as a rate over time (falls/year). Given the clinical importance of preventing falls while preserving physical activity, falls assessment integrated with activity measurement is recommended when determining whether a risk factor is associated with falls. J Am Geriatr Soc 67:87-92, 2019.

Keywords: aging; falls; glaucoma; physical activity; visual field.

Figure 1.

Cumulative incidence of falls and injurious falls

Figure 2.

Association between different rates of falls with degree of visual field damage and other patient characteristics. RR – rate ratio, p – p-value, IVF – integrated visual field, dB – decibels, yr – year, vs. – versus, Af. Amer – African American, Cauc – Caucasian, meds – medications. Associations presented in the figure all come from the same two models (one assessing fall/year as an outcome, the other assessing falls/step), except for the associations with inferior IVF, which come from additional multivariable models which evaluated inferior IVF sensitivity (and not total IVF sensitivity) as the primary independent predictor of the falls/year or falls/step.

Figure 3.

Association between different rates of injurious falls with degree of visual field damage and other patient characteristics. RR – rate ratio, p – p-value, IVF – integrated visual field, dB – decibels, yr – year, vs. – versus, Af. Amer – African American, Cauc – Caucasian, meds – medications. Associations presented in the figure all come from the same two models (one assessing injurious fall/year as an outcome, the other assessing injurious falls/step), except for the associations with inferior IVF, which come from additional multivariable models which evaluated inferior IVF sensitivity (and not total IVF sensitivity) as the primary independent predictor of the injurious falls/year or injurious falls/step.