Acceleration derived <b>3-day</b> measures of the <i>quantity</i> of walking in the fallers and non-fallers.

<p>These measures were calculated only from activity bouts ≥1 min, from the AP axis</p>*<p>The measures in this table were not statistically different in the fallers and non-fallers.</p>†<p>Measures which were not distributed normally according to the Kolmogorov-Smirnov test and were, therefore, analyzed using the Mann-Whitney test.</p><p>a Measures which were not normalized to the entire recording duration or activity duration.</p><p>Note: None of these measures were significantly different in the fallers and non-fallers.</p

Survival curve showing the time to first fall among all subjects who reported no falls in the year prior to the study.

<p>Based on fall history, all of these subjects had a relatively low risk of future falls. However, the anterior-posterior width of the peak in the frequency domain, a measure of gait variability derived from the 3-day recording, was associated with time to first fall. When subjects were classified as those having a relatively high (above the median) or low (below the median) width, those with a high width experienced a fall sooner (Log rank test: p = 0.0034, Wilcoxon test: p = 0.0029), compared to those with a relatively low width.</p

Acceleration derived <b>3-day</b> measures of the <i>quality</i> of walking in the fallers and non-fallers.

<p>* Measures which were significantly different in the fallers and non-fallers. We performed the Hochberg-Benjamini method for multiple comparison analysis for each of the 3 locomotor constructs separately: vertical (V), anterior posterior (AP), and medio-lateral (ML). P-values less than or equal to 0.043 (V), 0.012 (AP) and 0.00 (ML) were considered statistically significant in the 3 different constructs in the present analyses.</p>†<p>Measures which were not distributed normally according to the Kolmogorov-Smirnov test and were, therefore, analyzed using the Mann-Whitney test.</p

Examples of vertical acceleration signals of a PD faller (left) and a non-faller (right).

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone-0096675-g001" target="_blank">Figure 1A</a> shows a 3-day raw acceleration signal. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone-0096675-g001" target="_blank">Figure 1B and 1C</a> show the time and frequency domains of a 30 second signal (derived from the raw signal), respectively. The acceleration pattern of the PD faller (male, 61 yrs old) is less smooth compared to the PD non-faller (male, 74 yrs old) (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone-0096675-g001" target="_blank">Figure 1B</a>). The peak amplitude of the dominant frequency is lower and wider in the faller compared to the non-faller, indicating of a less consistent, more variable gait pattern (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone-0096675-g001" target="_blank">figure 1C</a>). <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone-0096675-g001" target="_blank">Figure 1D</a> shows an example of 3-day vertical acceleration signal in the frequency domains. The PD faller has a less consistent gait pattern, as reflected by the lower amplitude and wider spectrum. Similar findings are observed on a group level (recall <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone-0096675-t003" target="_blank">Table 3</a>).</p

Survival curve showing that gait speed while off was not significantly associated with the time to first fall (Log rank test: p = 0.688, Wilcoxon test: p = 0.697) among subjects who reported no falls in the year prior to testing.

<p>Please compare to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone-0096675-g003" target="_blank">Figure 3</a>.</p

Associations between the 3 day sensor-derived measures and performance-based measures of fall risk.

<p>The p-values were corrected for multiple comparisons according to the Hochberg-Benjamini method. We performed the correction for each of the 3 locomotor constructs separately: vertical (V), anterior posterior (AP), and medio-lateral (ML). P-values less than or equal to 0.017 (V), 0.015 (AP) and 0.003 (ML) were considered statistically significant in the 3 different constructs respectively in the present analyses.</p

Time spent in different activities in a PD faller and non-faller (right).

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone-0096675-g002" target="_blank">Figure 2A</a> shows a general, descriptive example of the time spent walking, standing, lying and sitting in two subjects as a function of time over the 72 hour recordings. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone-0096675-g002" target="_blank">Figure 2B</a> shows the percent time spent in each of these activities. Note that on a group level, walking amounts were similar in the fallers and non-fallers (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone-0096675-t002" target="_blank">Table 2</a>). Please note that although this figure is based on previously validated measures <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone.0096675-vanHees1" target="_blank">[57]</a>, we do not extract any quantitative measures from it. The figure is included here to illustrate how the present approach can be extended further in future work. In the current study, the analyses focused on walking bouts that were one minute or longer in order to robustly identify walking and, ultimately, the quality of these walking bouts (recall the methods and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096675#pone-0096675-t002" target="_blank">Table 2</a>).</p

Visual rating of White Matter Hyperintensities according to Schelten et al.

<p>Deep White Matter Hyperintensities (DWM); Periventricular Hyperintensities (PVH).</p

An example of periventricular WMHs in two patients with the PIGD subtype and two patients with the TD subtype.

<p>As shown, a subject with PIGD had a low score on the Scheltens scale, while another had a relatively high score (5 out of max. possible 6). Similarly, one patient in the TD group had a low score, while another had a relatively high score. These examples are consistent with the lack of an association between the Scheltens’ scoring and PIGD and TD subtypes that was seen in general.</p

Correlations between Schelten’s scoring of WMHs and PIGD and TD symptom.

*<p>Entries are Pearson’s correlation coefficient and the associated p-value. Deep White Matter Hyperintensities (DWM); Periventricular Hyperintensities (PVH).</p