Background
Falls are common, with up to 30% of community dwelling and 50% of institutionalized older adults falling every year [
1]. It has been reported that as many as 10% of falls result in major injury often leading to institutionalization and death. In Australia alone, there has been a four-fold increase in the number of deaths resulting from falls since 2002; this is thought to be due to the aging population, with women accounting for over half of deaths due to falling [
2].
Advanced age, mobility, sensory and medical factors, cognitive capacity, certain medications, and environmental hazards are known risk factors for falls among older adults [
3]. Another possible risk factor for falls is depression. It has been shown to precede falls in the elderly, and is also a possible outcome of falls, as with increased anxiety, decreased satisfaction with life and activity restriction [
3,
4]. Psychotropic medications also increase risk of falls [
5], possibly due to their sedative nature, and thus are a potential mediator of the relationship between psychiatric disorders and falls. However, the exact underlying mechanism(s) of action for the relationship between psychiatric disorders and falls remains unclear. Moreover, it is uncertain whether the relationship occurs among younger adults or those residing within the community, rather than in institutions.
As such, we aimed to investigate the association between depressive and anxiety disorders, psychotropic medication use, and falls in a large, randomly-selected, population-based sample of women spanning the full adult age-spectrum. We also aimed to examine the role of potential confounders in accounting for any observed associations.
Discussion
The findings of this cross-sectional, population-based study across the adult age spectrum showed that women meeting criteria for 12-month depression had an increased risk of falling compared to those with no history of depression independent of anthropometric, demographic, medical and lifestyle factors. Psychotropic use was also confirmed as an independent risk factor for falls; but, interestingly neither past depression nor anxiety disorders were associated with falling.
These findings are concordant with recent meta-analyses of prospective studies reporting depression to be independently associated with increased odds of recurrent falls in older people [
1,
3]. Studies investigating this relationship in samples of community-dwelling and institutionalised older people have repeatedly reported positive findings. Within a population-based sample of 7,414 elderly women, depressive symptomatology was associated with up to a 40% increased odds of falling, which persisted after adjustment for socio-demographic characteristics, medical conditions, functional status, medication use and other lifestyle factors [
13]. Similarly, depressive symptoms, as measured with a 4-item Geriatric Depression Scale, were shown to be associated with recurrent falls in a large group of community dwelling elderly [
14]. Utilising a random sample of Medicare claimants (n = 601,922) from Australia, the odds of a fall- related injury was found to be approximately two times greater for elderly men and women with depression [
15]. In a prospective cohort study of community-dwelling older people examining predictors of recurrent falls, depression was considered to be as strong a predictor as abnormal postural sway, two or more falls in the previous year, and low scores for hand grip strength [
16]. While increased worry and fear of falling in older people has been repeatedly shown [
4], the relationship between anxiety disorders and falls is less explored. In contrast to our findings, Whitney et al. found anxiety as measured by the Goldberg Anxiety Scale to be a significant predictor of falling as was poor attention and orientation, increased postural sway with eyes closed, and antidepressant use in a group of cognitively impaired older adults [
17]. Another study found the prevalence of anxiety (and depression) to be higher among fallers [
18].
These data are consistent with previous findings that psychotropic medication is associated with falls [
5]. A recent meta-analysis of 71 studies containing data on risk factors associated with psychotropic drug use among the elderly reported the pooled OR for the association between falls and any psychotropic use to be 1.78 (95% CI 1.57-2.01) [
5]. An earlier meta-analysis of studies conducted between 1966 and 1996 reported a similar pooled OR of 1.73 (95% CI, 1.52-1.97) [
19]. Both antidepressants and benzodiazepine use alone have been associated with increased falling in the elderly. In the recent aforementioned meta-analysis, antidepressant and benzodiazepine use was associated with a 1.66 (95% CI, 1.4-1.95) and 1.48 (95% CI, 1.23-1.77) fold increased risk of falls, respectively [
5]. Dose response relationships are evident, whereby falls rates among nursing home residents have been shown to increase with increasing daily doses of antidepressants [
20,
21] and benzodiazepines with greater half-lives [
22]. Examining the time course of falls to identify specific at-risk periods during antidepressant treatment, Joo
et al. [
23] found of the 104 elderly participants, 40 (38%) fell during the 21 weeks of treatment, with about half (53%) falling during the first six weeks, indicating falls monitoring is warranted during the acute stages of treatment. Similarly, when comparing new and repeat use of benzodiazepines, Maxwell
et al. [
24] reported an increased risk of fall-related hospitalisation for new users of benzodiazepines (OR 2.8, 95% CI 2.2-3.6) and tranquillisers (OR 2.0, 95% CI 1.5-2.6), with risk estimates reducing slightly for repeat users. Other psychotropic agents, including sedatives and hypnotics and antipsychotics, have also been associated with increased falls risk among the elderly [
25,
26].
Potential mechanistic factors used to explain the relationship between falls and psychiatric disorders include perturbations in gait, functional mobility, cognitive impairment, psychomotor retardation, changes in blood pressure and effects of psychotropic medication [
4]. However, in the present study involving individuals spanning the entire adult age range, psychotropic use, mobility, and blood pressure did not significantly influence the relationship between depression and falls. In general, depression has been shown to be associated with changes in gait, including decreases in walking speed, gait unsteadiness, and inability to maintain a stable walking pattern among the elderly [
27-
29]. In a study of 50 older patients diagnosed with either MDD or bipolar disorder, walking pace tended to be reduced and gait unsteadiness and swing time variability was increased; this predisposes individuals to falls [
30].
Postural instability may also play a role in the risk of falls. Within a group of 69 patients admitted to a geriatric hospital unit for ‘spontaneous’ unexplained falls during a 12-month period, impairment in postural abilities in the standing position was shown to differ between the depressed fallers group and non-depressed fallers group [
31]. The antidepressants paroxetine and sertraline have been associated with increased falls risk among older adults due to impairments in balance control and body sway [
32,
33], although another study in older adults found no acute changes in body sway after six weeks of treatment with sertraline [
34]. It is noteworthy that the possible risk imposed by gait changes appears to be a state rather than a trait marker of depression, as those with prior but not 12-month depression showed no increase in falls risk.
A major strength of this study is that it examined the relationship between psychiatric disorders and falls within a population-based sample spanning the entire adult age range. Previous research has been limited to the elderly, with the majority of studies involving samples of institutionalised participants. In our models, there was no age interaction, indicating the relationship between depression and falls was similar for young and older women. We recognise that this study has some limitations. Power limitations prevented exploration of the relationship between specific classes of benzodiazepines and antidepressants and falls. Furthermore, we excluded users of other psychotropic agents, including sedatives, hypnotics and antipsychotics, due to the sample size preventing additional subgroup analyses. Medication dose, duration of therapy, and stability are also potential confounders influencing outcomes; however, these variables could not be tested in our multivariate analyses. Likewise, rigorous measures of gait and balance were also not available to be tested. Last, as in all observational studies, there may have been unrecognised confounding.
Competing interests
LJW has received Grant/Research support from Eli Lilly, Pfizer, The University of Melbourne, Deakin University and the NHMRC.
JAP has received speaker fees from Amgen, Eli Lilly and Sanofi-Aventis and funding from the Geelong Region Medical Research Foundation, Barwon Health, Perpetual Trustees, The University of Melbourne, ANZ Charitable Trust, the American Society for Bone and Mineral Research, Amgen (Europe) GmBH, the BUPA Foundation and the NHMRC.
FNJ has received Grant/Research support from the Brain and Behaviour Research Institute, NHMRC, Australian Rotary Health, Geelong Medical Research Foundation and The University of Melbourne, and has been a paid speaker for Sanofi-Synthelabo, Janssen Cilag, Servier, Pfizer, Network Nutrition, Health Ed and Eli Lilly.
SLB has received Grant/Research support from The University of Melbourne and the NHMRC.
MB has received Grant/Research Support from the NIH, Simons Foundation, CRC for Mental Health, Stanley Medical Research Institute, MBF, NHMRC, Beyond Blue, Geelong Medical Research Foundation, Bristol Myers Squibb, Eli Lilly, Glaxo SmithKline, Organon, Novartis, Mayne Pharma, Servier and Astra Zeneca. He has been a paid consultant for Astra Zeneca, Bristol Myers Squibb, Eli Lilly, Glaxo SmithKline, Janssen Cilag, Lundbeck and Pfizer and a paid speaker for Astra Zeneca, Bristol Myers Squibb, Eli Lilly, Glaxo SmithKline, Janssen Cilag, Lundbeck, Organon, Pfizer, Sanofi Synthelabo, Solvay and Wyeth.
ALS, AGD, RH, HKH and PR have no conflicts of interest, including specific financial interests and relationships and affiliations relevant to the subject matter or materials discussed in the manuscript.
Authors’ contributions
LJW took part in the conception and design of the study, acquisition of the data, data cleaning, statistical analysis, interpretation of the data and took primary responsibility for writing the manuscript. JAP, ALS, FNJ, SLB, AGD and MB took part in the conception and design of the study, interpretation of the analysis and critically revised the manuscript. RH, HKH and PR took part in the interpretation of data and critically revised the manuscript. All authors read and approved the final manuscript.