If we want to understand Parkinson's or to be able to judge the effectiveness of potential therapies, we must measure symptoms. The issue that I want to address here is the frequency with which we take measurements.

Little et al. report [1]:
"Currently, there is a scarcity of objective clinical information about symptom dynamics at intervals shorter than 3 months stretching over several years, but Internet-based patient self-report platforms may change this."

While the measurement of symptoms, e.g. UPDRS, requires costly clinical involvement and time consuming attendance at a medical centre there is understandable reluctance to repeat the test frequently.

With automated, unobtrusive measurements, and with data communicated over the web, it is possible to take measurements every second or even more frequently.

To a certain extent getting more information off of a few people is equivalent to getting less information off of more people.

For instance, knowing that the performance of one person improved by 12% over a year, is less powerful than knowing that performance improved by 1% in each month of the year.

Reference

[1] J Med Internet Res. 2013 January; 15(1): e20.
"Quantifying Short-Term Dynamics of Parkinson’s Disease Using Self-Reported Symptom Data From an Internet Social Network"
Max Little, Paul Wicks, Timothy Vaughan and Alex Pentland

John