Table 2.

Summary characteristics of the longitudinal included studies.

Study and Country	Participants	Subtypes of PSP and criteria for PSP	Cognitive and Mood status	Assessment	Walking aids	Follow-up	Clinical motor utcomes/other outcomes	Objective gait outcomes	Objective balance outcomes	Author’s conclusion
Abate et al. (26) Italy	PSP: n = 35, age (68.1 ± 5.4 years), disease duration (4.2 ± 2.5 years), men (n = 27), women (n = 8)	MDS PSP criteria. Richardson’s syndrome (n = 28), parkinsonism predominant (n = 5), freezing of gait predominant (n = 2)	Not reported	PSPRS, Wearable sensors (one on the back and one on each foot)	Ten (29%) participants required unilateral support to complete at least one of the required tasks.	Three-month follow-up for PSPRS and each objective variable	PSPRS total score did not show a significant change over the follow-up (0.78% increase), but significant differences were detected for the “emotional lability” item (36.54% decrease) and the “arising from chair” item (16.31% increase). PSPRS total showed moderate inverse correlations with gait speed (r = −0.434; p < 0.001), and with stride length, swing and turning velocity, 360° angle and 360° turning velocity and moderate correlations with gait double support, stance and turning duration. PSPRS gait/midline subscore presented a strong inverse correlation with gait turning velocity, moderate inverse correlations with gait speed, stride length, swing, 360° angle, 360° duration and 360° turning velocity and moderate direct correlations with gait double support time and stance.	The analysis from baseline to 3-month follow-up showed that cadence and cycle duration from the 2-min walking test presented a significant increase over time (by 3.69 and 3.94% respectively).	Not reported.	Results from the study demonstrated the change of objective gait parameters over a short-term follow-up. Wearable sensors can provide an objective, sensitive quantitative evaluation and immediate notification of gait changes in PSP.
Ghosh et al. (27) United Kingdom	PSP: n = 23, age (71.1 ± 8.6 years), disease duration (3 years), men (n = 14), women (n = 9) Healthy Control: n = 22, age (71.4 ± 7.6 years), disease duration (N/A)	PSPRS Richardson’s syndrome	ACE-R = 76.4 ± 10.9 FAB = 10.8 ± 3.9 VOSP=7.6 ± 3.2	PSPRS, UPDRS-III, Saccadometry	Not reported	1.2 years for PSPRS, UPDRS-III, Saccadometry and cognitive status	PSPRS showed a mean change over a year of 11.3 points (p < 0.001). UPDRS-III showed a mean change of 8.3 points (p=0.003) and mu (the inverse median latency for saccades) showed a mean decrease of 0.4 s−1(equivalent to an increase in latency of 0.02 s) (p=0.01). Cognition did not change significantly during the study period.	Not reported	Not reported	Patients show significant deterioration over one year using the PSPRS severity measure. Oculomotor function changed over one year, including the range of vertical gaze in the PSPRS.
Pereira et al. (28) United Kingdom	PSP: n = 28, age [69.2 (52–68) years], disease duration [1.9 (0.2–6.3) years], men (n = 15), women (n = 12) Healthy Control: n = 28, age [66.2 (56–72) years], disease duration (N/A)	MDS PSP criteria. Subtypes not reported	MoCA = 22.4 (12–30) MMSE = 26 (20–30) Fluency test (Semantic) = 21.8 (6–41) Fluency test (Phonemic) = 19.9 (6–50)	PSPRS UPDRS-III	Not reported	1.5 years for PSPRS and MDS-UPDRS-III and cognitive status. Assessment visits were done every 3 months.	The increase in MDS-UPDRS-III was statistically significant after 12 months (Δ = 11.75, SD = 12.31, p < 0.008) while the increase in PSPRS became significant 15 months after baseline assessment (Δ = 7.42, SD = 7.63, p < 0.008). The MoCA and MMSE scores did not show any enduring changes in scores over time.	Not reported	Not reported	Motor decline in PSP is consistently captured by clinical rating scales. These results support the inclusion of multiple follow-up time points in longitudinal studies in the early stages of PSP.
Sotirakis et al. (29) United Kingdom	PSP: n = 17, age [63 (51–73) years], disease duration [1.6 (0–6) years], men (n = 9), women (n = 8)	MDS PSP criteria. Subtypes not reported	MMSE = 26.2 (20–30)	Kinematic gait and posture features collected by a body-worn IMU	Not reported.	1 year, over five visits at 3-month intervals.	Not reported.	There was a significant change in mean turn velocity, SD of Stride length and mean toe off angle. These three features served exclusively as predictors of progression on a mathematical model used to predict MDS-UPDRS-III and PSPRS-motor. Strongly significant differences from baseline were apparent 3 months earlier in these models than in the actual scores	Not reported.	Data from wearable IMU arrays coupled with mathematical modeling can be used to track progression of PSP, complementing established clinical rating scales. In this study, the reduced variability in the modeled data allowed a progression signal to be discerned 3 months earlier than would otherwise be expected.

ACE-R = Addenbrooke’s Cognitive Examination—revised; FAB = Frontal Assessment Battery; MDS-UPDRS-III = Movement Disorders Society Unified Parkinson’s Disease Rating Scale part III motor subscale score; MoCA = Montreal Cognitive Assessment; MMSE = Mini-mental State Examination; NINDS-SPSP: National Institute of Neurological Disorders and Society for Progressive Supranuclear Palsy criteria for PSP; PSPRS = PSP rating scale; UPDRS-III = Unified Parkinson’s Disease Rating Scale part III motor subscale score; VOSP=Visual Object and Space Perception Battery.