Table 2.

Model building strategy to measure EDI effect for 30-year disease duration.^a,b

Model	Formula	Number of regression parameters	Number of smoothing parameters	Effective degrees of freedom	Corrected Akaike Information Criteria
R-MS
M1	tensor(t,age) + sex	31	2	13.27	13,826.47
M2	tensor(t,age) + sex + s2(year of onset of symptoms)	35	3	16.10	13,811.33
M3	tensor(t,age) + sex + s1(EDI)	35	3	16.42	13,796.10
M4	tensor(t,age) + sex + s1(EDI) + s2(year of onset of symptoms)	39	4	18.61	13,780.76
M5	tensor(t,age) + sex + s1(EDI) + s2(t)∗EDI	39	4	17.59	13,792.95
M6	tensor(t,age) + sex + s1(EDI) + s2(year of onset of symptoms) + s3(year of onset of symptoms)∗EDI	43	5	21.07	13,780.19
PPMS
M1	tensor(t,age) + sex	31	2	11.44	4923.41
M2	tensor(t,age) + sex + s2(year of onset of symptoms)	35	3	12.14	4921.56
M3	tensor(t,age) + sex + s1(EDI)	35	3	14.17	4922.70
M4	tensor(t,age) + sex + s1(EDI) + s2(year of onset of symptoms)	39	4	14.93	4920.28
M5	tensor(t,age) + sex + s1(EDI) + s2(t)∗EDI	39	4	15.55	4924.43
M6	tensor(t,age) + sex + s1(EDI) + s2(year of onset of symptoms) + s3(year of onset of symptoms)∗EDI	43	5	16.02	4922.18

^aFor R-MS, the knots' locations for time were (0.1, 12.1, 16.8, 21.3, 25.6, 30.0), for age were (−19.5, −2.3, 5.2, 13.3, 39.2), for EDI were (−11.1, −2.6, −0.6, 2.0, 32.1) and for year of onset of symptoms were (−39, −9, 0, 7, 16). For PPMS, the knots' locations for time were (2.3, 10.1, 14.2, 18.6, 23.3, 29.9), for age were (−28.7, −7.3, 1.4, 7.8, 29.5), for EDI were (−8.3, −2.5, −0.6, 1.9, 28.6) and for year of onset were (−39, −8, 0, 6, 15).

^bA reading guide accompanying table to describe model building strategy is available in the Supplemental Materials.