Hazard analysis, Harms and UI design for the patient population

Context: We are designing software as a medical device for patients with Parkinson's Disease (PD). There are several known symptoms associated with PD such as tremors, gait/balance, mobility, cognitive decline. We know that we need to design our software in terms of UI/UX to account for these symptoms and generally elderly age. The question is related to the link between usability, users and risk management.

Question: Do we need to include the symptoms as harms in the hazard analysis (ISO 14971)? The symptoms of PD will affect the user interface specification of the device but our software device does not cause the harm itself.

Thoughts: We do need to include the symptoms as harms, because following this thread could lead to contraindications or change to intended purpose? But is this correct assumption because our device does not cause the harm? Appreciate your thoughts on this topic thanks!

In short, no. Do not include symptoms as harms in your HA. Harms are the injuries that can be caused by the device itself, either directly or indirectly. Including them would only make sense if your device could somehow exacerbate the condition(s).

The symptoms you described are simply characteristics about your intended user population that you must account for when designing your device. When it comes time to perform your summative usability analysis, you will want to make sure you include users with the symptoms you described, if those symptoms could impact the safety of your device.