Approximately 30% of community-dwellers and 50% of nursing home residents aged 65 years and older fall each year (Blake, Morgan, & Bendall, 1988
). Within the elderly population falls are a factor in approximately 10% of emergency room visits (Sattin, 1992
). Falls have significant negative outcomes on old individuals including physical injury (Bell, Talbot-Stern, & Hennessy, 2000
; Tinetti, Speechly, & Ginter, 1988
), hospitalization (Lachman, Howland, & Tennstedt, 1998
; Runge, 1993
), restricted mobility (Kosorok, Omenn, & Diehr, 1992
), nursing home admissions (Tinetti & Williams, 1997
), and death (Murphy, 2000
). The Center for Disease Control and Prevention reported unintentional injuries, with falls as the leading type, as the seventh leading cause of death in the United States in the 65 and over age group. Hence, understanding the causes and risk factors for falls is of significant public health importance.
The risk factors for falls are heterogeneous and include poor balance (Nevitt, Cummings, Kidd, & Black, 1989
), impaired gait (Tinetti et al., 1988
), musculoskeletal weakness (Prudham & Evans, 1981
), use of psychotropic drugs (Cumming, 1998
; Thapa, Gideon, & Cost, 1998
), impaired visual acuity (Tinetti et al., 1988
), and medical conditions such as Parkinson’s disease (Jantti, Pyykko, & Hervonen, 1993
), arthritis (Tinetti, Williams, & Mayewski, 1986
), and strokes (Dolinis, Harrison, & Andrews, 1997
Dementia is a significant risk factor for falls (Buchner & Larson, 1987
). However, the relationship between specific cognitive functions and the risk of falls in normal aging or in dementia is poorly understood. Furthermore, whereas multidisciplinary risk assessment and interventions of falls focus on gait, balance and strength (Tinetti, Baker, McAvay, Claus, Garrett, Gottschalk, et al., 1994
), neuropsychological assessment, with the exception of gross evaluation of dementia status, is conspicuously absent. Identifying associations between specific cognitive functions and falls in normal aging has significant implications as such findings would suggest that: a) neuropsychological assessment may provide incremental information relevant to risk assessment for falls b) specific cognitive functions may be etiologically related to falls c) shared neural substrate could be implicated in cognitive performance and specific motor outcomes such as falls.
The relationship between attention and falls has been assessed using dual-tasks with simultaneous cognitive and motor demands. This is exemplified by studies that required elder participants to walk and talk at the same time. Such studies revealed that dual-task performance costs, as measured in decrements in walking speed, were related to the risk of falls suggesting that limited attentional resources in older persons were causally related to falls (Camicioli, Howieson, Lehman, & Kaye, 1997
; Verghese, Buschke, Viola, Katz, Hall, Kuslansky, et al., 2002
). This choice of experimental approach is not surprising given that attentional resources that decline with age (Craik & Byrd, 1982
; McDowd & Shaw, 2000) are required for maintaining one’s posture and gait, especially in public where the ability to negotiate competing demands from the environment is paramount. Further, dual-task methodology provides a theoretical and empirical basis for evaluating divided attention (see Pashler, 1994
; Pashler, 1998
, for reviews of theories and empirical findings concerning dual-task paradigms). However, interpreting dual-task costs requires that the single tasks be well characterized and understood in terms of their cognitive demands (Holtzer, Stern, & Rakitin, 2005
). More recently we showed that empirically derived cognitive factors were differentially related to gait velocity in single and dual-task conditions in a large non-demented sample of older adults residing in the community (Holtzer, Verghese, Xue, & Lipton, 2006
). Specifically, factors that measured verbal IQ, Speed/Executive Attention and Memory were all related to gait velocity when performed as a single task. In contrast, only the Speed/Executive Attention and Memory factors were related to gait velocity in the dual-task (walking while talking). Further, the Speed/Executive Attention factor was the most potent predictor of gait velocity irrespective of gait task condition (Holtzer et al., 2006
). Walking and talking dual-task paradigms are useful predictors of falls. However, because gait performance shares variance with cognitive functions and is related to the risk of falls it is difficult to assess mechanisms using this model. Stated differently, it is difficult to separate cognitive from gait effects on falls using this paradigm. In contrast, independent assessment of cognition and gait affords statistical control of gait performance when evaluating associations between specific cognitive processes and falls.
Our previous findings (Holtzer et al., 2006
) characterized the relationship between cognitive functions (Verbal IQ, Executive attention, Memory) and locomotion in aging in single and dual-task conditions. The current study was designed to extend our previous findings and examine whether and how the same cognitive functions were related to falls. Additionally, a number of confounding variables may modulate the association between cognition and falls including demographic characteristics, medical conditions such as arthritis, stroke and Parkinson’s disease, and medication use (see Nevitt, 1997
, for review of risk factor for falls in aging). Accordingly, we used multivariate models to assess the associations between cognitive functions and falls after adjusting for potential confounders including quantitative and clinical measures of gait performance.
The current study aimed to identify, cross-sectionally, whether and how specific cognitive functions were related to falls in a large sample of elders who did not meet criteria for dementia or Mild Cognitive Impairments. To accomplish this goal, a comprehensive neuropsychological test battery validated for use with elder adults (Katzman, Aronson, Fuld, Kawas, Brown, Morgenstern, et al., 1989
; Masur, Sliwinski, Lipton, Blau, & Crystal, 1994
; Sliwinski, Buschke, Stewart, Masur, & Lipton, 1997
) was submitted to factor analysis. The resultant orthogonal factors represented separate and empirically defined cognitive domains (Verbal IQ, Speed/Executive Attention and Memory). We used three parameters to evaluate falls within the last year. First, we defined a group of fallers who had one or more fall events in the past year as well as the complimentary group of non-fallers. Second, because recurrent falls are more likely to be indicative of pathology than a single fall, we divided the group of fallers into two sub-groups. Individuals who reported only one fall event comprised the Single Fall subgroup. Individuals who reported two or more fall events comprised the Recurrent Falls subgroup. We hypothesized that Speed/Executive Attention would be associated with falls. However, we also assessed whether associations between different cognitive functions and falls varied depending on whether single or recurrent falls were the outcome variables.
Finally, the current study controlled for the possible confounding effects of clinical gait abnormality and quantitative measures of gait on the associations between cognitive functions and falls.