dc.description.abstract |
Background: Falls and subsequent injuries among older adults (65 years and over) are a major
public health issue contributing to increased morbidity and mortality. Risk factors for falls
among older adults have been examined extensively over the years. However, there is a dearth
of literature regarding risk factors for falls among middle-aged adults (50 – 84 years) − the age
where the trajectory for fall rates starts to increase.
Aim and Objectives: The main aim of this thesis is to identify the risk factors for any type
(injurious and non-injurious), injurious, and recurrent falls among community-dwelling midand older-adults aged 50- 84 years in New Zealand (NZ).
Methods: A systematic review examined the published literature on risk factors for falls among
community-dwelling mid- and older-adults aged 50 years and over which informed the design
of the main analytical component of the thesis.
A secondary analysis was carried out on data collected as part of the Vitamin D Assessment
(ViDA) study; a randomised, double-blind, placebo-controlled trial that recruited 5,108 adults
aged 50-84 years in Auckland with over three years of follow-up. Data analysed included
sociodemographic, lifestyle characteristics, and medical conditions collected at the ViDA
baseline assessment. Prescription data came from the NZ Ministry of Health
Pharmaceutical Information Database. Follow-up data on self-reported falls was collected
from questionnaires mailed initially monthly, and then 4-monthly, to the home of ViDA
participants. Descriptive analyses summarised the distribution of baseline characteristics and
prescription medications. A univariate analysis utilising t-tests and chi-square tests was
conducted to investigate the cumulative fall risk (for any type of fall, injurious falls and
recurrent falls) during follow-up for participants according to different exposure levels. For
cohort analysis, cox proportional hazards and negative binomial regression (plus mean
cumulative function analysis) were used to examine the risk factors for the fall types of interest.
A test for interaction analysis was utilised to compare the relationship between factors across
the three outcome measures of interest. Directed Acyclic Graphs (DAG) were constructed to
assist with interpreting results and identifying interactions between variables and fall outcomes.
Results: 152 studies met the literature review inclusion criteria. Risk factors were classified
into five domains: socio-demographic, lifestyle, physical, medical conditions, and
pharmaceutical risk factors. The key findings revealed the following as risk factors for falls: age, sex, ethnicity (White), living alone, marital status, poor self-rated health, depression,
diabetes, stroke, angina, arthritis, pain, history of fracture, history of falls, respiratory diseases
(asthma, emphysema and shortness of breath), benzodiazepines, antiepileptic/anticonvulsant
medications, antidepressants, psychotropic medications, analgesics, diuretics, and respiratory
medications. While Black/African American was shown to have a protective effect against
falls.
Cohort analyses of the outcome ‘any type of fall’ were carried out on 5,049 participants after
excluding those who did not return a fall questionnaire during follow-up (n=52) or who were
missing time to first fall (n=7). Analyses of the outcomes ‘injurious fall’ and ‘recurrent falls’
were caried out on 5,053 participants after excluding those who did not return a fall
questionnaire during follow-up (n=52) or were missing time-dependent variables (time to
injurious fall/total no. of recurrent falls data, n=3).
Factors associated with increased hazard ratios [HR] of having any fall (all types including
injurious) were female sex [HR 1.44, p<0.0001], living alone [HR 1.16, p=0.01], stroke and/or
transient ischemic attack (TIA) [TIA only; HR 1.28, p=0.03], fall history [HR 1.77, p<0.0001],
decreased confidence to do daily activities without falling [Quite Confident: HR 1.33,
p<0.0001], arthritis [HR 1.10, p=0.03], previous fracture (or broken bone) [HR 1.10, p=0.03],
asthma [HR 1.16, p=0.01], depression [HR 1.34, p<0.0001], antiepileptic medication [HR 1.26,
p=0.02], antidepressants [HR 1.16, p=0.03], and anti-Parkinson medication [HR 1.94, p=0.02].
Medication affecting the renin angiotensin system (ARAS) and education level were the only
protective factors associated with reduced hazard of any fall [HR 0.85, p=0.001].
For injurious falls, significant risk factors included female sex [HR 1.48, p<0.0001], living
alone [HR 1.21, p=0.0004], employment [retired; HR 1.15, p=0.01], stroke and/or angina [TIA
only; HR 1.43, p=0.01], fall history [HR 1.76, p<0.0001], decreased confidence to do daily
activities without falling [Quite Confident; HR 1.33, p<0.0001], arthritis [HR 1.11, p=0.03],
previous fracture (or broken bone) [HR 1.13, p=0.01], asthma [HR 1.15, p=0.02], depression
[HR 1.31, p=0.0002], and anti-Parkinson medications [HR 2.09, p=0.003]. Ethnicity (South
Asian) [HR 0.63, p=0.004] and current smoking [HR 0.79, p=0.02] were the only factors
associated with reduced hazard of injurious falls.
Factors associated with increased incidence rate ratios [IRR] of recurrent falls included female
sex [IRR 1.17, p=0.0003], living alone [IRR 1.22, p= 0.0001], employment (retired) [IRR 1.24,
p<0.0001], heart attack and/or angina [Angina only; IRR 1.25, p=0.02], stroke and/or TIA [TIA only; IRR 1.47, p=0.0003], fall history (last four weeks) [IRR 1.92, p<0.0001], decreased
confidence to do daily activities without falling [Quite, IRR 1.49, p<0.0001; Not at all, IRR
2.14, p<0.0001], chronic pain [IRR 1.23, p<0.0001], depression [IRR 1.24, p=0.002],
antidepressants [IRR 1.18, p=0.01] and anti-Parkinson’s medications [IRR 4.07, p<0.0001].
Factors associated with reduced incidence rate of recurrent falls were ethnicity (South Asian)
[IRR 0.64, p<0.0001] and BMI (underweight and overweight) [IRR 0.40, p=0.01; HR 0.86,
p=0.002 respectively].
A test for interaction indicated that the hazard/rate of falls was consistent across all three fall
outcomes, and the following are the most significant risk factors for falls among mid and older
adults in NZ: sex (female), living alone, employment (retired), angina, TIA, fall history (last
four weeks), arthritis, previous fracture, chronic pain, asthma, depression, antiepileptic
medication, antidepressants, and anti-Parkinson medication; while ethnicity (South Asian),
education (secondary), current smokers, and BMI (under-weight and overweight) were
significantly protective against falls across all three fall outcomes. DAG diagrams were created
for all variables that were included in the final multivariable models, which provided a clear
picture of mediators and confounding factors that may impede the association of certain factors
with falls. These variables (i.e., marital status) were then not included in the final multivariable
models.
Conclusion: This study indicates that risk factors for falls (any, injurious and recurrent) among
mid and older community-dwelling older adults are complex and multifaceted. In addition to
traditional risk factors identified, other factors not commonly researched − such as asthma, TIA
only, anti-Parkinson’s medications, and antiepileptic drugs − were shown to be associated with
significantly increased risk of falls; while ethnicity (South Asian) and current smokers were
shown to have a reduced fall risk in this population sub-group. This is the first cohort study to
use pharmaceutical dispensing data to examine the association between certain medications
such as psychotropic, antipsychotics, laxatives and fall risk. The findings indicate that older
adult fall prevention strategies need to commence in middle age, and consideration needs to be
given to addressing novel factors in future risk prevention strategies. Additional research is
required to reaffirm the association between medical conditions and specific medication classes
on fall risk and to understand why there is a lower risk of falls among South Asian population
groups. |
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