Falls are a common problem for older people

Falls are a common problem for older populations, with considerable consequences for the individual and health-care systems. One in three people over the age of 65 will fall each year, with higher rates in older age groups, residents of aged care facilities, and clinical populations, such as those with Parkinson’s disease.[1] Falls are the leading cause of injury-related hospitalization in people aged over 65 years, and they account for 14% of emergency admissions in this age group.[2] Falls can result in restriction of activity and fear of falling, decreased mobility, reduced quality of life, and loss of independence. Falls also account for about 40% of injury-related deaths in older people.[3]

Half of the falls reported by community-dwelling older people occur within their homes and surrounding areas. Most occur on level surfaces in commonly used rooms such as the kitchen, living room, and bedroom. With increasing age and frailty, fewer falls occur outside the home, reflecting the increased time spent indoors. Whereas some falls involve an external trigger such as a slippery floor or cracked pavement, many do not involve obvious environmental hazards.[4] Falls in older people most often occur during tasks of locomotion or transfer.[5, 6] Community-dwelling older people report that up to 75% of falls occur due to trips, slips, or loss of balance.[7]

Risk factors for falls

Falls were once considered to be random unavoidable events, but it is now known that falls can be predicted to a certain extent. As falls are often the result of a complex interaction between an individual’s physical functioning, their behavior, and the environment, perfect prediction of falls is unlikely. However, a range of demographic, psychosocial, physiological, and medical risk factors for falls have been identified.[1] Demographic and psychosocial factors associated with an increased risk of falling include advanced age, limitations in activities of daily living, fear of falling, depression, and a history of previous falls. Impaired vision and impaired cardiovascular function also increase the risk of falls.

Balance and mobility problems are particularly strong risk factors for falling in older people.[8] People with neurodegenerative and musculoskeletal conditions affecting balance and mobility such as stroke, Parkinson’s disease, cognitive impairment, arthritis, foot problems, and chronic pain have higher rates of falling.[1] Other physiological risk factors for falls include impaired muscle strength, poor reaction time, impaired lower limb sensation, and poor vision,[1] so people with conditions affecting these such as cataracts and diabetes are also at a high risk of falling. Furthermore, declines in sensorimotor function or hemodynamic stability associated with age, inactivity, medication use, or minor pathology increase the risk of falls in older people without documented medical illness.

Gait impairment is prevalent in older people and associated with poor outcomes

Walking difficulties are highly prevalent in older people. One in three people in the United States, aged 65 and older, report difficulty walking three city blocks or climbing one flight of stairs.[9] The prevalence of observed gait impairment increases with age. The incidence of abnormal gait, defined by clinicians following visual inspection, was found to be 25% in people aged 70–74 and increased to almost 60% in those aged 80–84.[10]

Abnormal gait has been associated with greater risk for adverse outcomes in older people, including immobility, falls, dementia, morbidity, institutionalization, and mortality,[10–12] with greater impairment associated with increased risk. Abnormal gait patterns may be an early indicator of subclinical disease, as they are associated with an increased risk of cardiovascular disease, dementia, musculoskeletal and other diseases.[10, 13] For example, gait disorders have been shown to predict the onset of non-Alzheimer’s dementia with a hazard ratio of 3.5.[14] However, abnormal gait is not an inevitable part of aging as approximately 20% of very old people show completely normal gait.[13]

The spinal cord executes rhythmical and sequential activation of muscles for locomotion, which is influenced by afferent information from multiple sensory channels for modulation of the motor output. Appropriate integration of afferent input and coordination of force generation is important for steady and efficient locomotion. Since aging is associated with declines in sensory acuity and neuromuscular function, it is not surprising that gait changes with increasing age. Furthermore, central processes are important for initiation, termination, and adaptation of gait. Indeed, the control of gait seems to become more cognitively demanding with age. Older adults tend to walk slower and more cautiously than younger people, differences interpreted as adaptations for improved stability and safety. These patterns are more evident in older people who have previously fallen.

Gait impairments are central to common clinical conditions

Gait difficulties are commonly experienced by people with cognitive impairment and dementia and medical conditions including neurological, musculoskeletal, cardiac, and respiratory conditions. Gait disorders are also more common in older people in acute hospital and residential aged care facilities.[11]

Observational gait analysis

Observational assessment of gait can be used in clinical settings and includes observation of walking at a natural and fast pace, walking in tandem (heel-to-toe), gait initiation behavior, and turning. An example is the Tinetti Performance-Oriented Assessment of Gait, designed to assist in clinical gait analysis, consists of nine areas of gait observation: gait initiation, step height, step length, step symmetry, step continuity, path deviation, trunk stability, walking stance (step width), and turning while walking.[59]

The Einstein Aging Study (EAS) conducted clinical examinations in almost 500 community volunteers aged 70–99 years, during which gait was observed.[10] Study clinicians determined that 35% of people had “abnormal gait,” with approximately half being further subtyped as neurological in nature and the other half considered non-neurological. Neurological gait impairments commonly included unsteady/ataxic gait (almost half showed marked swaying or losing balance while walking, tandem walking, or turning); hemiparetic (one-quarter showed a leg swinging outward), frontal (one in eight people had short steps, wide base, and difficulty with foot lift), and parkinsonian (one in ten people demonstrated shuffling steps, stooped posture, absent arm swing, en bloc turns, and/or festination), found to be due to nervous system lesions, including neuropathies and stroke. Non-neurological gait impairments were commonly due to joint (85%), cardiac (10%), or respiratory (6%) problems. The features of non-neurological gait abnormalities were not described, but they are likely to have included slowed walking speed, step length asymmetry, and reduced range of motion.

Biomechanics of aging gait and falls

With increased age is a tendency to walk slower, with shorter step length, wider step width, and increased time in double-support.[60] Prospective studies also show significantly slower velocity and increased proportion of stride time spent in double-support in people who subsequently fall, compared with those who did not fall in the following year.[61] Prospective fallers are likely to have physical limitations, such as muscular weakness, that result in gait changes, or they may adapt their gait pattern with an awareness of their unsteadiness and fear of falling. Some early gait changes with aging may be compensated for in order to maintain walking speed. For example, some older people walk with reduced step length, but increase their cadence (rate of stepping) to maintain gait velocity.

It is likely that the control of gait in older adulthood declines due not only to deterioration in physical capacities, but also to the deterioration of cognitive efficiency in integrating sensory information for the precise regulation of the motor pattern. Walking can be an attention-demanding task, as evidenced by dual task studies that show gait to be adversely affected while simultaneously performing a cognitive task. Older age and poorer cognitive function are both associated with slowed walking while conducting a concurrent cognitive task.[62] Increased variability in gait parameters has also been shown with increased age,[63] and fall risk, including stride and swing time [64] and foot-lift asymmetries.[65] A more variable gait may indicate poorer neuromuscular control and might increase the risk of falling due to inaccuracies in foot trajectories.

Gait slowness has been shown to predict fall risk, cognitive health, physical health, and even death in older people;[66–69] therefore, gait speed is an important clinical measure in the aged care setting. Gait speed is easily measured by timing a walk over a known distance. The instructions (either walk comfortably or as fast as you can), the length of the walk, and the type of the gait measured (e.g., constant velocity walking) are important considerations.

Changes with age in kinematic (movement) and kinetic (force) gait parameters are numerous and include reduced hip and ankle motion,[70–74] reduced ankle power generation,[73, 75, 76] increased mechanical energy demands of lower limb musculature,[77–79] poorer control of footstrike;[66, 80] and a larger toe-out angle.[70, 75, 81] However, many of these are related to a slower walking velocity and shorter stride length in older, compared with younger people. Independent of walking speed, reduced hip extension angles [64] and increased anteroposterior heel contact velocity in older people [80] have been identified, which may increase the propensity to slip.[75, 82]

A prospective study of older people showed differences in kinematic and kinetic gait parameters in those who subsequently fell. Kemoun et al. examined gait patterns in 54 healthy older adults who had not previously experienced a fall.[61] Those who fell in the following 12 months walked with significantly reduced ankle range of motion and delayed dorsiflexion prior to heel strike, which might predispose to tripping. Indeed, the floor-toe clearance at mid-swing is reduced in older people, 11 mm for older adults compared with an average 13 mm for young adults,[60] increasing the risk of tripping. At the hip, future fallers, compared with nonfallers, had significantly reduced range of motion, a reduced flexion moment, and less power absorbed for energy return during the swing phase. Kerrigan et al. also found previous fallers exhibited reduced peak hip extension, compared with nonfallers.[83] These differences are likely to be related to slower walking speeds. Similarly Lee et al. measured walking kinetics in previous fallers and nonfallers.[84] Despite the fact that the fallers walked at half the speed, significant increases were found in their peak moments for hip flexion, hip adduction, knee extension, knee adduction, ankle dorsiflexion, and ankle eversion. Reduced power absorption at the knee and associated increased power absorption at the ankle indicates a poorer ability to efficiently control motion at these joints.

Biomechanics of trips and slips

Up to half of the falls in older people are attributed to tripping.[26, 43, 85–87] A trip induces a forward rotation of the body over the base of support, requiring a response to arrest the forward angular momentum of the body. Numerous studies have induced trips in the laboratory to study appropriate behaviors and limiting factors to successful recovery following a trip (for review, see [88]). Two different strategies to compensate for an induced trip have been identified.[89, 90] When the trip occurs in early swing phase, a lowering strategy is predominantly used, in which the tripped foot is quickly lowered to the ground and the contralateral foot initiates a recovery step. When the trip occurs in late swing phase, an elevating strategy is seen, in which the tripped limb is subsequently elevated over the obstacle in an attempt to continue the step. A slower walking speed is associated with an improved recovery following a trip [91] and may be one reason why older adults adopt a slower gait pattern for enhanced safety.[75]

The support limb is of great importance for successful recovery of balance following a trip.[31] A strong push-off reaction, prior to the recovery (stepping) limb contacting the ground enables time and clearance for correct positioning of the recovery limb. Furthermore, appropriate generation of joint moments in the support limb can help to arrest the angular momentum of the body. When properly placed, the recovery limb can also generate a force and moment that counteract the body angular momentum.[91] A slower development of mechanical responses seems to be a major factor limiting older adult’s recovery from trips and other balance perturbations. Furthermore, older adults are less capable of adapting their gait (turning, sidestepping, stopping) to avoid an obstacle. Compared with young adults, they slow down, take more steps, and are less successful with shorter response times,[92] which is likely to lead to trips and falls.

Slips are another common gait-related mechanism of falls in older people that often result in injury due to the large impact forces. A slip occurs when the base of support moves relative to the body (forward translation of the foot), reducing the foot contact deceleration forces, leading to a backward rotation of the body. The incidence of slip initiation may be similar between young and older adults, yet older adults seem to have slower and less effective recovery responses than young adults; they slip longer and faster, and fall more often,[82] which may be due to age-related changes in vision, reaction time, and muscle strength.[93] Falling is more likely to occur with increased gait speed, increased forward heel displacement, increased posterior displacement of the body’s center of mass relative to the base of support, and a larger angle of the leg relative to the ground (representative of a longer step length prior to the slip).[94]

Interventions to prevent falls in community-dwelling older people

There is now strong evidence from randomized controlled trials that falls in older people living in the community can be prevented by well-designed intervention programs.[95] Effective interventions include targeted risk factor assessment and modification as well as a number of single interventions directed at the general community (exercise), high-risk individuals (home safety assessment and modification), and those with particular risk factors (removal of cataracts, reduction of psychoactive medication use, and podiatry intervention for those with foot pain).

Exercise programs have been found to prevent falls when delivered in group or home-based settings,[95] and exercise that targets balance has been found to have a greater fall prevention effect.[96] In the general community, falls can be prevented by exercise among people with identified risk factors for falls as well as in people without identified risk factors (i.e., from programs simply targeting the general older community).[95]

Exercise interventions can enhance gait in certain clinical groups

It is known that exercise interventions can improve gait for people with a range of clinical conditions. Systematic reviews of randomized trials show us that physiotherapy interventions and treadmill training can enhance gait in people with Parkinson’s disease,[97, 98] and that a circuit class approach to therapy delivery and the use of treadmill training can enhance gait soon after stroke.[99] Findings of systematic reviews of trials of interventions to improve gait, and mobility more broadly, after hip fracture and stroke have been more mixed but individual trials have had promising findings.[100, 101] For example, a circuit class using “task-related” exercises (such as stepping, standing up, and reaching outside the base of support while standing) improved gait speed in long-term stroke survivors.[102] Gait speed and the need for walking aid use after hip fracture was improved by intensive outpatient physiotherapy and exercise training.[103] Further investigation is needed to establish optimal approaches to gait enhancement in people with different clinical conditions, keeping in mind the relative costs and benefits of different approaches.

The effectiveness of exercise-based fall prevention interventions in people with health conditions requires further investigation

Unfortunately, the prevention of falls in older people with particular health conditions known to increase the risk of falls is less clear. For example, the Otago exercise program involves the tailored prescription of home exercises that challenge balance and strength. It is an effective falls prevention program and, importantly, falls injury prevention strategy in older people recruited through general practices but does not appear to have similar fall prevention effects in people with severe visual impairment.[104, 105] Similarly, although they enhanced mobility, a circuit-based exercise program did not prevent falls in stroke survivors,[102] and a home exercise program did not prevent falls in frail older people or those with recent hospital stays.[106, 107] However, in those with milder neurological disease, who are probably more similar to the general community dwellers, subgroup analysis has found that exercise as a single intervention strategy does appear to prevent falls.[102, 108]