Surveying the Dietary Intake, Physical Activity Patterns, Muscle Strength and Morphology of Adults With Inclusion Body Myositis

This study will employ an observational, case-control design.

A sample size of 32 participants with inclusion body myositis (IBM) has been determined based on a power calculation designed to detect a strong association (r = ±0.5) between dietary protein practices and various outcome measures related to muscle mass and function. Using a two-tailed test with an alpha level of 0.05 and power of 80% (β = 0.2), the analysis indicated a required sample size of 29 participants. The sample size equation used was appropriate for Pearson's Correlation analysis. To account for an estimated 10% dropout rate, the final target recruitment number is 32. In addition, 15 age- and activity-matched control participants will be recruited. Power calculations for comparisons between IBM and control groups returned lower sample size requirements, reflecting the lower variability typically observed in healthy populations.

Identification of participants with IBM will be carried out at the Tertiary Neuromuscular Service, Salford Royal Hospital (Manchester, UK), and the Neuromuscular Centre (Winsford, Cheshire, UK). Those identified will be approached in clinic or by email with a Participant Information Sheet, the study poster and a Consent to Contact Form. The completed Consent to Contact Form will allow the Manchester Metropolitan (ManMet) research team to follow up with an invitation to a screening visit at the ManMet Institute of Sport (IoS)- a phone call or email. Control participants will be recruited from the local community. If agreed, a phone call will take place to arrange a screening and enrolment visit.

The screening visit to the IoS will last up to 1.5 hours but may end prematurely if the participant is found to be ineligible. During the visit, participants will meet with a researcher who will provide a detailed explanation of the study, including time commitment, risks, and participant rights. Informed consent will then be obtained. Participants will then complete four questionnaires to highlight any contraindications to testing and ensure appropriate matching between the disease and control group. These include: a Demographic and General Health Questionnaire, the sIBM Physical Functioning Assessment, an MRI Safety Checklist and the Physical Activity Scale for Individuals with Physical Disabilities. At the end of this visit, participants will be fitted with two activity monitors secured using medical-grade adhesive (one on the wrist and one on the thigh). They will also be given a paper-based food record or shown the Libro App that will serve as a digital alternative, and a set of questionnaires.

Participants will then complete a four-week home-based monitoring period. During this time, they will wear the activity monitors continuously for seven days to record physical activity, sedentary behaviour, and sleep patterns. They will also complete two 3-day food diaries, spaced three weeks apart, to capture dietary intake (food and drink, excluding water). Additionally, participants will complete a Food Frequency Questionnaire, which asks how often different food items have been consumed over the past year. Throughout this period, participants will also complete the series of validated questionnaires at their own pace. These include a Quality of Life Questionnaire (Short Form-36v2) for overall health and wellbeing, the Nottingham Extended Activities of Daily Living (NEADL) Scale for independence in daily activities, the Modified Fatigue Impact Scale (MFIS), the Visual Analogue Scale (VAS) for pain, the Pittsburgh Sleep Quality Index (PSQI), and the SWAL-QOL questionnaire, which assesses how swallowing impacts quality of life.