Functional disability and health-related quality of life
Physical and mental health functioning were based,
respectively, on the physical and mental component
summary scores of the SF-12.27 Impairment was evaluated
with the SDS.28-31 Substantial impairment for each
SDS subscale was defined by a rating of 7 or higher.
The effect of symptoms on work productivity was also
assessed using 2 self-reported questions.