Table 2

Relative risk of hospital-treated pneumonia by vitamin E supplementation in participants initiating smoking at ≤ 20 years, ATBC Study 1985–1993


Intervention
 Effect of vitamin E


Vitamin E
 No vitamin E
Subgroup
 No. of participants
 No. of cases
 Rate*
 No. of cases
 Rate*
 RR (95% CI)*
All
 21657
 370
 6.0
 331
 5.3
 1.14 (0.98–1.32)
Weight (kg) †





     36–59
 1054
 47
 16.7
 32
 10.4
 1.61 (1.03–2.53)
     60–69
 4115
 79
 6.7
 68
 5.7
 1.17 (0.84–1.62)
     70–89
 12495
 182
 5.1
 187
 5.1
 0.99 (0.81–1.22)
     90–99
 2653
 39
 5.2
 34
 4.5
 1.17 (0.74–1.86)
     100–154
 1328
 22
 5.7
 9
 2.5
 2.34 (1.07–5.08)
β-Carotene





     No
 10842
 204
 6.6
 169
 5.4
 1.22 (0.99–1.50)
     Yes
 10815
 166
 5.4
 162
 5.2
 1.04 (0.84–1.30)

* Rate is given as the number of pneumonia cases per 1,000 person-years. Risk ratio (RR) was estimated using the proportional hazards regression model comparing participants who received vitamin E and those who did not. No covariates were included in the models, because the comparison is between large randomized groups. The sizes of the compared intervention groups are the same within 10% accuracy in the lowest and highest body-weight groups, and within 2% in the other comparisons. The uniformity of the vitamin E effect was tested by adding a dummy variable for vitamin E effect in the 36–59, 60–69, 90–99 and 100–154 kg groups, allowing each of the four groups their own vitamin E supplementation effect. The regression model was improved by χ2(4 df) = 7.76, P = 0.10, compared to the model with a uniform vitamin E effect. Adding the vitamin E effect only in the 36–59 and 100–154 kg groups improved the model by χ2(2 df) = 6.79, P = 0.034, compared to the model with a uniform vitamin E effect.

† Weight was missing for 12 participants; two of them had pneumonia, one in the vitamin E group and one in the no-vitamin E group.

Hemilä and Kaprio Nutrition Journal 2008 7:33   doi:10.1186/1475-2891-7-33

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