Table 3.
Complete overview of evaluated studies according to number and study type, the evidence levels derived, and consensus-based levels of recommendation according to topic
| Area | Number and type of study | Evidence levels | Recommendation levels |
|---|---|---|---|
| Breastfeeding | 0 MA, 1 RCT, 7 CS, 0 CC, 3 CSS | 1x1b, 7x2b | A |
| Maternal diet during pregnancy and/or lactation | 0 MA, 5 RCT, 15 CS, 0 CC, 0 CSS | 5x1b, 15x2b | A and B |
| Breast-milk substitutes in at-risk infants | 0 MA, 2 RCT, 2 CS, 0 CC, 0 CSS | 2x1b, 2x2b | A |
| Introduction of solid foods and infant diet up to the age of 1 year | 1 MA, 2 RCT, 8 CS, 3 CC, 5 CSS | 2x1b, 8x2b, 3x3b | A and B |
| Diet after the age of 1 year and body weight | 2 SR, 0 RCT, 4 CS, 2 CC, 7 CSS | 4x2b, 2x3b | A |
| General diet and vitamin D: during pregnancy/lactation and up to the age of 1 year | 2 SR, 1 RCT, 4 CS, 3 CC, 4 CSS | 1x1b, 2x2b, 3x3b | - |
| Effects of probiotics and prebiotics | 3 SR, 15 RCT, 1 CS, 1 CC, 0 CSS | 15x1b, 1x2b | - |
| Keeping pets | 2 SR, 0 RCT, 3 CS, 0 CC, 1 CSS | 3x2b | B |
| House dust mites | 0 MA, 0 RCT, 3 CS, 1 CC, 2 CSS | 3x2b, 1x3b | A |
| Mold and dampness | 3 MA, 0 RCT, 3 CS, 1 CC, 0 CSS | 3x2a, 3x2b, 2x3b | B |
| Exposure to tobacco smoke | 0 MA, 0 RCT, 2 CS, 0 CC, 1 CSS | 2x2b | A |
| Vaccination | 0 MA, 1 RCT, 1 CS, 0 CC, 2 CSS | 1x1b, 1x2b | A |
| Motor vehicle emissions | 0 MA, 1 RCT, 0 CS, 0 CC, 3 CSS | 4x2b, 2x3b | B |
| Non-specific immune modulation | 1 SR, 0 RCT, 4 CS, 0 CC, 5 CSS | 4x2b | - |
| Pharmaceutical drug use | 1 SR, 1 RCT, 4 CS, 1 CC, 5 CSS | 1x1b, 4x2b, 1x3b | - |
| Psychological factors | 0 SR, 0 RCT, 1 CS, 0 CC, 1 CSS | 1x2b | - |
| Childbirth | 1 SR, 0 RCT, 2 CS, 0 CC, 1 CSS | 2x2b | - |
| In total | 12 SR, 4 MA, 29 RCT, 64 CS, 12 CC, 4 CSS | 28x1b, 3x2a, 66x2b, 14x3b | - |
CC, case-control study; CS, cohort study; MA, meta-analysis; RCT, randomized controlled study; SR systematic review; CSS, cross-sectional study