Table 4.
HR with 95% CI of having unfavourable outcomes, by smoking habits post diagnosis (non-smokers, postdiagnosis quitters and postdiagnosis continued smokers)
| Smoking status | N | Years (SD) | Outcome (%) | HR (95% CI)* | aHR (95% CI)† |
| First clinical disease worsening | |||||
| Non-smokers | 1311 | 6.8 (4.5) | 671 (50) | 1.0 (reference) | 1.0 (reference) |
| Quitters | 72 | 7.4 (5.1) | 39 (54) | 1.01 (0.73 to 1.40) | 1.01 (0.73 to 1.39) |
| Continued smokers | 315 | 6.5 (4.7) | 168 (53) | 1.13 (0.96 to 1.34) | 1.21 (1.03 to 1.44) |
| EDSS 3 | |||||
| Non-smokers | 1048 | 8.2 (4.7) | 334 (32) | 1.0 (reference) | 1.0 (reference) |
| Quitters | 63 | 9.0 (5.2) | 21 (33) | 0.96 (0.61 to 1.49) | 0.95 (0.61 to 1.50) |
| Continued smokers | 249 | 7.9 (4.9) | 109 (44) | 1.42 (1.15 to 1.77) | 1.45 (1.16 to 1.81) |
| EDSS 4 | |||||
| Non-smokers | 1048 | 9.6 (4.4) | 153 (15) | 1.0 (reference) | 1.0 (reference) |
| Quitters | 63 | 10.5 (4.8) | 8 (13) | 0.80 (0.41 to 1.63) | 0.90 (0.49 to 1.65) |
| Continued smokers | 249 | 9.8 (4.5) | 47 (19) | 1.28 (0.92 to 1.77) | 1.40 (1.01 to 1.96) |
| Physical worsening (increased MSIS-29 physical score by 7.5 or more) | |||||
| Non-smokers | 1058 | 5.6 (4.3) | 425 (40) | 1.0 (reference) | 1.0 (reference) |
| Quitters | 56 | 5.8 (4.2) | 28 (50) | 1.23 (0.84 to 1.81) | 1.23 (0.83 to 1.82) |
| Continued smokers | 244 | 6.0 (6.7) | 118 (48) | 1.21 (0.99 to 1.49) | 1.26 (1.02 to 1.56) |
| Psychological worsening (increased MSIS-29 psychological score by 7.5 or more) | |||||
| Non-smokers | 1056 | 5.3 (4.4) | 512 (48) | 1.0 (reference) | 1.0 (reference) |
| Quitters | 56 | 5.8 (4.4) | 30 (54) | 1.03 (0.71 to 1.49) | 1.05 (0.72 to 1.52) |
| Continued smokers | 242 | 5.1 (6.6) | 149 (62) | 1.42 (1.18 to 1.71) | 1.52 (1.26 to 1.83) |
| Cognitive disability worsening (decreased SDMT Score by 8 or more) | |||||
| Non-smokers | 1079 | 5.9 (3.3) | 287 (27) | 1.0 (reference) | 1.0 (reference) |
| Quitters | 57 | 5.4 (3.4) | 16 (28) | 1.14 (0.69 to 1.89) | 1.14 (0.68 to 1.91) |
| Continued smokers | 252 | 6.1 (3.5) | 80 (32) | 1.16 (0.91 to 1.49) | 1.40 (1.09 to 1.81) |
*Crude.
†Adjusted for age at diagnosis, sex, disease phenotype, disease duration, baseline EDSS, disease-modifying therapy, passive smoking and snuff use.
EDSS, Expanded Disability Status Scale; MSIS-29, Multiple Sclerosis Impact Scale 29; SDMT, Symbol Digit Modalities Test.