General clinical and demographic characteristics of the study population by disease duration and age at onset
| Variable | Study cohorts of disease duration | ||
|---|---|---|---|
| 20–22 years (N=320) | 23–25 years (N=168) | ≥26 years (N=108) | |
| Males, N (%) | 186 (58) | 92 (55) | 56 (52) |
| History of smoking, N (%) | 79 (25) | 39 (23) | 26 (24) |
| Education (years), mean [SD] | 8 [4] | 8 [4] | 8 [5] |
| Family history for PD, N (%) | 63 (20) | 29 (17) | 25 (23) |
| Disease duration (years), mean [SD] | 21 [1] | 24 [1] | 30 [4] |
| Age at onset of disease (years), mean [SD]—All | 49 [9] | 47 [9] | 42 [9] |
| Age at onset <50 years, N (%) Mean [SD] | 145 (45) 42 [6] | 93 (55) 42 [7] | 85 (79) 39 [7] |
| Age at onset ≥50 years, N (%) Mean [SD] | 175 (55) 56 [5] | 75 (45) 55 [4] | 23 (21) 55 [4] |
| Age at assessment (years), mean [SD]—All | 70 [9] | 71 [8] | 72 [8] |
| Age at onset <50 years | 63 [6] | 66 [7] | 69 [6] |
| Age at onset ≥50 years | 77 [5] | 78 [4] | 82 [4] |
PD, Parkinson's disease.