Abstract
We sought to assess the quality of life in PD patients before the diagnosis, in comparison to age-matched individuals free of PD, among participants in two large prospective cohorts of men and women. Components of the Short-Form Health Status Survey (SF36) were administered to all participants in 1996 and 2008 in the Health Professionals Follow-up Study (HPFS), and in 1992, 1996, 2000 and 2004 in the Nurses' Health Study (NHS). We used scores in 7 health-related quality of life-dimensions, that were rated from 1(worst) to 100(best) points. We fitted a multivariate mixed-effect model with repeated measures to estimate the expected decline with age and compared that to the decline observed among PD cases by time to diagnosis. 454 men and 414 women with PD contributed data to the analyses. A decline in physical function in PD patients relative to the whole cohort began approximately 7.5 years prior to diagnosis in women and 3 years prior to diagnosis in men, and continued to decline thereafter with a rate of 2.35 and 1.43 points per year in women and men respectively (p < 0.001 for both). For comparison, the average yearly decline in individuals without PD was 0.42 and 0.23 points per year in women and men respectively. Other measures of quality of life (only available in women) declined in a similar pattern to physical function. In summary, the quality of life in PD patients begins to decline years before the diagnosis.