Table 2 Relative risk of MS according to baseline intake of vitamin D for NHS (1980–1998) and NHS II (1991–1999)

ParametersNHS*NHS II*Pooled*Pooled
Median IU/dCases/person-yRR (95% CI)Median IU/dCases/person-yRR (95% CI)RR (95% CI)RR (95% CI)
* Adjusted for age in 5-y groups.
† Further adjusted for smoking (never, <10 packs/y, 10–24 packs/y, 25+ packs/y) and latitude at birth.
MS = multiple sclerosis; NHS = Nurses’ Health Study; RR = relative risk.
Total vitamin D
    Quintile 15817/320,108Ref.12820/149,878Ref.Ref.Ref.
212421/320,4601.24 (0.65–2.35)21726/149,8991.30 (0.72–2.34)1.27 (0.83–1.96)1.28 (0.83–1.98)
319715/321,0470.89 (0.44–1.77)31718/150,0440.90 (0.47–1.70)0.89 (0.56–1.43)0.89 (0.56–1.43)
434414/319,0140.81 (0.40–1.65)47217/150,1870.87 (0.46–1.64)0.84 (0.52–1.35)0.83 (0.52–1.35)
56419/318,6520.55 (0.25–1.22)74216/150,0690.77 (0.40–1.50)0.67 (0.40–1.12)0.69 (0.42–1.15)
76/1,599,28197/750,075
    p trend0.050.220.030.03
    p heterogeneity0.42
Vitamin D from food
    Quintile 14914/319,365Ref.11019/149,803Ref.Ref.Ref.
210017/320,4961.21 (0.59–2.45)17715/149,9680.79 (0.40–1.55)0.97 (0.60–1.57)0.97 (0.60–1.58)
314718/320,0591.29 (0.64–2.61)23430/149,9331.58 (0.89–2.81)1.46 (0.94–2.27)1.47 (0.94–2.30)
420414/320,2011.01 (0.48–2.13)30218/150,1300.95 (0.50–1.80)0.97 (0.60–1.59)0.97 (0.60–1.58)
531113/319,1590.93 (0.43–2.00)41415/150,2430.78 (0.39–1.54)0.84 (0.51–1.40)0.84 (0.51–1.40)
76/1,599,28197/750,075
    p trend0.610.560.440.42
    p heterogeneity1.0
Vitamin D from supplements, IU/d
    0064/1,120,418Ref.063/436,790Ref.Ref.Ref.
    < 4002285/153,4680.53 (0.21–1.33)22816/147,3260.75 (0.43–1.29)0.68 (0.42–1.08)0.68 (0.43–1.08)
    ≥ 4004007/325,3940.39 (0.18–0.85)40018/165,9600.75 (0.44–1.26)0.59 (0.38–0.91)0.60 (0.39–0.92)
76/1,599,28197/750,075
    p trend0.0070.200.0060.009
    p heterogeneity0.16