Patients and methods
The study was conducted in five nursing facilities, involving 88 subjects in total, i.e. 44 subjects with MCI (mean age of 83.8 years; 34 women (77.3%) and 10 men (22.7%)) and 44 healthy controls unaffected by MCI (mean age 81.67 years; 38 women (84.4%) and 7 men (15.6%)).
The following inclusion criteria were applied: age (> 65 years), absence of neurological or auditory deficits (i.e. a history of stroke with visible functional deficits of the locomotor system, sciatica, cerebral injuries), regular use of glasses with a power not exceeding 4 dioptres, and a Mini–Mental State Examination (MMSE) score of less than 24 points, although not less than 18, Barthel scale < 40 points . These criteria were supplemented by those proposed in the study by Winblad et al. . Furthermore, any elderly individuals who were found unable to complete any of the functional ability tests, were at that point pronounced non-eligible for further attendance in the study protocol.
Representativeness was calculated using a sample-size calculator:
For a population of 500,000 (a proportion of 0.5, and a standard error of 5.1), in conjunction with the 1.5 odds ratio (OR) for a decrease in the gait speed in the group affected by MCI, the determined representative population sample size was 44 subjects (MCI group), and 44 subjects unaffected by MCI (healthy controls group). The subjects were recruited by the onsite specialists employed in each nursing facility. Sociodemographic data of the individuals affected by MCI were acquired from their medical records. In the case of healthy controls, the data were acquired directly from the subjects. The variables addressing individual functional ability were presented as the data characterising both the study and the control groups. The testing protocol was executed by a trained physiotherapist boasting a minimum 2-year hands-on working experience with the elderly patients, and prior experience in pursuing academic research projects.
Prior to the actual commencement of the study protocol, the subjects were verbally introduced to its practical specifics. A general presentation was made, whereas the key points of the testing procedure were shown in the form of pictograms. All applicable constraints for the execution of the tests were fully compliant with the breakdown provided further below.
At the First Session, pertinent sociodemographic data were collected, followed by the assessment of individual cognitive abilities against the MMSE. The score acquired in the MMSE test was a qualifier for further attendance in the study protocol. In practical terms, if an individual failed to score within the 18–23 points range, he was pronounced non-eligible for further participation in the study protocol.
Subsequently, Timed Up and Go Test (TUGT), TUGTMAN, and TUGTCOG were completed. Single- and dual-task tests were carried out 3 times, whereas the mean score was ultimately recorded.
The Second Session comprised the 10 Meter Walk Test (10MWT) tests, both in the regular, and the fastest version, Strength of Lower Limbs and Fear of Falling (FOF), were also assessed.
The Third Session comprised the execution of 3 Single Leg Stance Open Eyes (SLS OP) and Single Leg Stance Closed Eyes (SLS CL) tests.
The examination of participants remaining in institutional care lasted 1.5 h in total, 30 min per each session.
Healthy subjects were tested in their own place of residence, in full compliance with the procedure outlined further above.
All participants were granted a 3–5 min period of rest between respective tests assessing individual functional performance. Subjects were assessed 2 h after a meal, in the morning hours.
Cognitive functions were assessed through MMSE, also known as the Folstein test, which facilitates assessment of five cognitive functions, i.e. orientation, memory, concentration, language, and constructional praxis .
The corresponding criterion for inclusion into the study group was the score ranging 18–23 points, as per applicable guidelines in the literature on the subject, indicative of mild cognitive impairment . The test was completed by a trained physiotherapist, under the same conditions for each subject.
Gait performance assessment under the single- and dual-task conditions
The version of TUGT test proposed by Podsiadlo was used to evaluate gait performance under the single-task conditions . The subjects were advised that the correct way to perform the test was to stand up from a chair and then walk a 3-m distance behind the line, then turn around, walk all the way back, and sit down in the chair. The walk should be completed at the fastest possible pace deemed safe by the test subject. Under the dual-task conditions, gait performance was assessed by means of yet another version of the TUGT test, i.e. the one modified in line with Shumway-Cook and Wollacotte . Dual-task activities were divided into the two types, i.e. motor-motor tasks (manual TUGT – TUGTMAN) and motor-cognitive tasks (cognitive TUGT – TUGTCOG). Both types of activities were performed following verbal and non-verbal instructions given by a physiotherapist.
During the TUGTMAN test, the subjects were asked to perform the same task as the TUGT test, while holding a beaker filled up with water in their dominant hand, whereas with regard to the TUGTCOG test, the subjects were supposed to incrementally count down by 7, starting off with a randomly selected number between 20 and 100, while walking. During either type of the dual-task test (TUGTMAN and TUGTCOG), a physiotherapist did not indicate which task had a higher priority. All timings were taken with the aid of a mobile phone (Apple iPhone 6 – model A1586), and a built-in stopwatch application with an accuracy of 0.01 s. A drop in the performance of dual-task activities was considered clinically significant, when the DTC, expressed as the relative difference between the gait speed under the dual-task conditions and that under the single-task ones, and then calculated in line with the formula given by Bock, was higher than 15% . In conformity with the algorithm proposed by Bock, an average DTC for healthy elderly individuals amounted to 15%, having effectively been calculated out of 13 different dual-task activities; the same criterion was consequently assumed in this study protocol .
The gait speed corresponding to either the single-task, or the dual-task conditions was determined by dividing the distance covered during the TUGT, TUGTMAN and TUGTCOG tests by the respective time it took to do so.
These tests were selected in view of being comprised of four essential components directly aiding the research effort, as well as offering the possibility of assessing a scope of ADLs:
1. Exclusion of the learning effect (TUGT test is performed first).
2. Very high test reproducibility .
3. An opportunity to assess short-term memory and metastability of attention during complex activity.
4. This test assesses the ability to stand up, walk, turn around, and sit down, i.e. an essential component in an individual pursuit of the ADLs.
Gait speed was calculated with the aid of the 10MWT, whereby the subject had to walk a distance of 10 m. In line with the test methodology, the first and the final metre were excluded from the measurements . Additionally, the two gait speeds were measured, i.e. normal, everyday speed, and the fastest speed the subject felt comfortable with.