Multiple sclerosis (MS) is a chronic, often disabling, neurologic disease, common among adults worldwide and in the US.1 It has a heterogeneous geographical prevalence with higher rates reported in Central and Northern Europe, North America, and Australia than for Asia, Africa, and South America.2 There are believed to be over 400,000 persons with MS in the US and 2.1 million worldwide. The majority of people with MS are typically diagnosed between 20 and 50 years of age, and women are affected two to three times more often than men. The exact cause of MS is not clear, but it is believed to result from a combination of genetic and environmental factors.3
This disease process involves intermittent bursts of focal inflammation across the central nervous system (CNS).4 The inflammatory process results in the demyelination and transection of axons throughout the CNS. The resulting damage leads to conduction delays and blockage of action potentials along nerve axons.4 This interference with neuronal conduction throughout the nervous system is associated with a heterogeneous array of functional impairments and symptoms including (but not limited to) muscle weakness, cognitive impairment, sensory disturbances, and a decline in postural control and gait function.1
Given these symptoms it is not at all surprising that falls are common in persons with MS. Indeed, over 50 % of persons with MS report falling over a 6-month period.5–8 Perhaps more alarming, the majority of those who do fall require medical attention for injuries.9,6,10 For example, persons with MS are four times more likely to suffer a hip fracture brought about by a fall than age- and gender-matched peers without MS.11 This elevated fracture risk stems from low bone mineral density and osteoporosis in persons with MS.12,13 Lastly, persons with MS who have previously fallen report worse physical and psychologic health status (i.e. health-related quality of life [QoL]) compared with nonfallers with MS.7
Falls can further have an adverse impact on fear of falling and falls selfefficacy and contribute to activity curtailment, physiologic deconditioning, loss of independence, and institutionalization.14,15 For instance, approximately 64 % of persons with MS have an increased fear of falling and, of those individuals, 83 % reported activity curtailment.16 Another study documented that approximately 75 % of community-dwelling persons with MS who have fallen in the last 6 months self-reported activity restriction due to concerns about falling.15 Recently, these self-reports of activity curtailment in persons with MS who have fallen were confirmed with objectively measured ambulatory physical activity (e.g. accelerometry). Specifically, persons with MS who had fallen in the last year had lower amounts of physical activity than persons with MS who had not fallen.17
One caveat to consider when reviewing the majority of research concerning consequences of falls in persons with MS is that all of the studies that support this disability-disuse cycle are cross-sectional in nature. Consequently, it is unclear whether falls truly lead to decreased activity and physiologic deconditioning as proposed or rather falls are unrelated to activity, physiologic deconditioning, and QoL. Ideally, the best way to determine whether there is a strong relation between these variables in persons with MS would be to conduct longitudinal investigations. If such an association is noted, we would further propose that it is worthwhile to explore the possibility that physical activity promotion18 can counteract the fall-related decline in physical activity and potentially minimize physiologic deconditioning and reductions in QoL.
There is sufficient evidence to conclude that persons with MS are at elevated risk for falls compared with healthy individuals of a similar age and that falls seemingly have significant negative effect on QoL stemming from physical injury and reduction in participation. Such observations underscore the importance of identifying risk factors for falls in MS. The main risk factors, if modifiable, can become the focus of targeted interventions designed for reducing falls and the life-altering effects on secondary outcomes such as compromised QoL and/or participation.
Fall Risk Factors in Persons with Multiple Sclerosis
The first step to fall risk prevention in any given clinical population involves an understanding of those factors that can contribute to such occurrences. This is necessary for both identifying individuals at risk for future falls and also for providing information that can be used to design appropriate therapeutic interventions that target a reduction in fall occurrence. Such an approach has been widely adopted in the gerontology literature that serves as a backdrop for the discussion of falls risk and prevention in persons with MS.19
Accordingly, we highlight major observations from the well-developed and characterized falls literature among older adults, another population that has considerable risk for falls. One of the most important observations is that falls are preventable with interventions designed to target specific risk factors.19,20 While previous studies have reported upward of over 400 potential fall risk factors for older adults,21 the primary risk factors include sensorimotor function, general balance, and walking ability.22,23 Linked to these factors is the evidence that highlights that impairments in muscle strength and coordination are also strong predictors of falls in older adults.21,24–27 Not surprisingly, interventions that target these specific factors have been the most widely developed and implemented. Overall, these interventions have been found to effectively reduced physiologic falls risk and fall incidence in older adults.19,20,24,27
It is important to note that although the geriatric literature offers important insights in terms of falls in the older adult, there are notable differences between persons with MS and healthy older adults regarding specific risk factors leading to falls. For instance, assessment of falls risk using standard tools developed for geriatric populations such as the physiologic profile assessment (PPA) illustrate that the overall risk for a future fall is greater for persons with MS than older adults (see Figure 1). Indeed, persons with MS without a fall history have a higher risk for falls even than older adults who have not fallen. This observation highlights the need to develop disease/patient specific falls risk models.