Slow-SPEED-United Kingdom: A Double-Blind Randomised Feasibility Trial of a Remote Gamified Physical Activity Programme in Adults With Hyposmia.

Slow-SPEED UK is an 18-month, randomised, double-blind, parallel-group feasibility trial evaluating the feasibility, acceptability, and safety of a digitally supported physical activity programme in community-dwelling adults aged 40 and over with objectively confirmed hyposmia (reduced sense of smell) and low baseline physical activity. The study is not designed or powered to assess clinical efficacy or disease outcomes.

Participants are identified through two routes: the PREDICT-PD research platform at Queen Mary University of London, and the Smell and Taste Clinic at James Paget University Hospital NHS Foundation Trust. Potential participants undergo telephone pre-screening followed by confirmatory olfactory testing using the 40-item University of Pennsylvania Smell Identification Test (UPSIT). Those scoring at or below the 15th percentile for age and sex are classified as hyposmic. Eligible individuals then enter a 4-week run-in period during which habitual daily step count is measured using a Fitbit Charge 6. Only those averaging fewer than 7,000 steps per day over at least 21 valid days proceed to randomisation. If recruitment falls below 70% of target after the first two months, and subject to Sponsor approval and REC amendment, the eligibility threshold may be broadened to fewer than 10,000 steps per day.

Eligible participants are randomly assigned 1:1 to one of two arms using sequentially numbered opaque sealed envelopes, stratified by age, sex, baseline activity level, and severity of smell loss. Double-blinding is maintained by presenting all activity goals within the smartphone application as relative percentage targets rather than absolute step values, ensuring neither participants nor investigators are aware of group allocation during the study period.

Both arms use the Slow-SPEED smartphone application integrated with the Fitbit Charge 6 wearable activity tracker. The intervention arm targets a progressive increase in daily step count up to 100% above individual baseline, with weekly goals increasing by 5% increments. The active control arm targets a 10% increase above baseline, with weekly goals increasing by 0.5% increments. Both arms use the same application structure, automated feedback, goal progression algorithm, and motivational features, including gamification, visualised progress, and optional non-directive motivational prompts. All participants also complete assessments using the Roche Mobile Application V2 (remote motor tasks performed every 6 weeks throughout the study period) and wear an Axivity AX6 accelerometer for 7-day bursts at baseline, 9 months, and 18 months.

Assessments are conducted at three time points: baseline (in-person), 9 months (remote), and 18 months (in-person). Baseline and 18-month in-person visits include olfactory testing (UPSIT), blood pressure measurement using standard sphygmomanometry, clinical motor assessment (MDS-UPDRS Part III), digital motor tasks (BRAIN test, Digital Finger Tapping, Manus Neurodynamica digital pen, NeuroClues eye-tracking), and a structured battery of questionnaires covering physical activity (LAPAQ), mood and anxiety (HADS), sleep quality (PSQI), quality of life, autonomic symptoms (SCOPA-AUT), and cognitive screening (MoCA). The 9-month remote assessment includes questionnaires and remote digital task completion. Physical activity is measured continuously throughout the study period via the Fitbit Charge 6.