Table 1.
Characteristics of the MZ twins clinically discordant for MS
| Characteristic | MS-affected MZ co-twins | Non-affected MZ co-twins | Range | p b |
|---|---|---|---|---|
| Number of pairs | 45 | 45 | ||
| Gender (female/male) | 32/13 | 32/13 | ||
| Age at study entry (years) | 42.3 ± 12.1 | 42.3 ± 12.1 | (21–67) | |
| Age of disease onset (years)a | 27.9 ± 8.4 | (14–46) | ||
| Years clinically discordant for MS at sample collectiona | 15.3 ± 11.1 | (1–45) | ||
| EDSS at study entry | 3.3 ± 2.3 | (0–9.5) | ||
| Pairs longer than 10 years clinically discordant for MS | 25 (56%) | |||
| Pairs with a positive family history of MS | 13 (29%) | |||
| MS type | ||||
| - RRMS | 31 (69%) | |||
| - SPMS | 12 (27%) | |||
| - PPMS | 2 (4%) | |||
| Smoking status | ||||
| Smoking at disease onset | 23 (51%) | 19 (42%) | 0.53 | |
| Pack-years at disease onset | 0.03 (0–3.5) | 0 (0–3.8) | 0.81 | |
| Smoking at sample collection | 14 (31%) | 12 (27%) | 0.82 | |
| Pack-years at sample collection | 0.6 (0–10.8) | 0 (0–6.3) | 0.24 |
Continuous data expressed as: mean ± standard deviation or median (interquartile range). Categorical data expressed as: number of observations (%)
EDSS Expanded Disability Status Scale, PPMS primary-progressive MS, RRMS relapsing-remitting MS, SPMS secondary-progressive MS
aSee Supplementary Fig. 1 for boxplots (with all data points) showing the distribution of the age of disease onset and the years that the MZ twins were clinically discordant for MS at sample collection
bMS-affected versus non-affected MZ co-twins calculated using a two-tailed Wilcoxon signed-rank test for continuous data and two-tailed Fisher’s exact test for categorical data