Data Collection
Education was dichotomized into primary/secondary and tertiary levels. Height and weight were measured, allowing body mass index (BMI) to be calculated. The number of doctor-diagnosed chronic conditions was obtained from the following: heart attack, heart failure, or angina pecto- ris; cataracts; stroke; diabetes mellitus; lung disease; asthma; arthritis; osteoporosis; cancer; Parkinson’s disease; peptic ulcer; hip fracture; hypertension; and high choles- terol. Number of regular medications was also recorded. Depression was assessed using the 20-item Center for Epidemiologic Studies Depression Scale (CES-D), on which scores of 16 or greater represent clinically relevant depres- sive symptoms.18
Mobility was assessed with the TUG using a chair with armrests and a seat of height of 46 cm. Participants were asked to rise from the chair, walk 3 m at normal pace to a line clearly marked on the floor, turn around, walk back to the chair, and sit down again. Walking aids were allowed if required, and no instructions were given about the use of participants’ arms. The time taken from the command “Go” to when the participant was sitting with their back resting against the back of the chair was recorded using a stopwatch. In addition to TUG, gait was assessed using a 4.88-m electronic walkway with embed- ded pressure sensors (GAITRite; CIR Systems, Inc., Haver- town, PA). Participants started and finished 2.5 m before and after the walkway to allow for acceleration and decel- eration. Average gait speed was calculated from two walks performed at normal pace. Participants underwent a comprehensive cognitive assessment including two tests of global cognition—the MMSE19 and the Montreal Cognitive Assessment (MoCA).20 A number of cognitive tests were used to assess function in four cognitive domains (executive function, processing speed, attention and memory); see Table 1 for full details of these tests. Most cognitive tasks assess more than one domain, but for the purposes of this study, each test was classified according to the main cognitive compo- nent (Table 2). The Color Trails Test was used as an alternative to the Trail-Making Task because it removes any cultural or language bias.21 Color Trail 1 mainly reflects visual scan- ning and processing speed, and Color Trail 2 requires visual scanning, attention, and mental flexibility, making it an executive function task. The clock and cube drawing tasks were extracted from the MoCA as additional mea- sures of executive function and visuospatial skills. Partici- pants also completed two verbal fluency tasks, which measure expressive language and executive function. These tests assess the ability to devise a strategy to search for and list words (e.g., categories of objects, verbs, words with similar letters), switch between these categories, and use short-term memory to keep track of the words that have already been recited.22 Sustained attention is also an executive function requiring arousal and the ability to focus attention on and process specific stimuli over a prolonged period of time. It is required to focus on an activity for long enough to complete a cognitively planned activity, any sequenced action, or any thought. It is assessed using the Sustained Attention to Response Task (SART).23 The choice reaction time test used a computer based program to assess concentration and processing speed. Cognitive reaction time was the time taken to release a button in response to a stimulus. Prospective memory, which is defined “as remember- ing to do something at a particular moment in the future or as the timely execution of a previously formed inten- tion”24 (p. 25) was also assessed and requires attention, memory, and executive function. Episodic memory was assessed using a word recall test. Visual reasoning and visual memory were assessed using the visual reasoning and picture memory tests from the Revised Cambridge Examination for Mental Disorders of the Elderly.25 The visual reasoning test also measures executive function.