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An investigation into trends of peanut allergy incidence in the last 15 years in England using sequential childhood cohorts.
Project Code: T07034
Institute of Medicine, Health and Social Care, University of Portsmouth
Research Requirements Document (Issue 8, April 2002) stated that in the light of Department of Health’s COT report (published in 1998) on peanut allergy, there is a need to establish whether the advice offered in the report has led to a change in incidence of peanut allergy. In addition there is a requirement to establish what impact, if any, this advice has had on the maternal consumption of peanut during pregnancy and breast-feeding.
This project utilised three cohorts of children born on the Isle of Wight over a 12-year period to address this area. Using a prospective cohort approach with a validated food frequency questionnaire, maternal dietary intake during pregnancy and breast-feeding were assessed. 445 (47.5%) women reported complete avoidance of peanuts, another 57 (6.1%) did not exclude peanut but never actually ate any and 360 (38.4%) did eat peanut. It is quite likely that women who reported complete avoidance were actually exposed to traces/hidden nuts. The majority of the pregnant women consumed milk (88.7%) and wheat (91.5%) frequently and white fish moderately (83.5%). With regards to egg intake, the question on egg intake showed a low validity and reliability and was therefore not included.
Data collected during the breast-feeding period indicated that in total, 265/614 (43.1%) mothers avoided one or more foods from their diets. These included a wide variety of foods such as the major food allergens, citrus, meat, spicy foods, onion, brassica family, shellfish and strawberries. Of the 265 mothers, 173 avoided some of the main allergenic foods, with 39 avoiding more than one of the main food allergens. We investigated the influence of maternal diet during pregnancy and breast-feeding on FHS and sensitisation in the infant during the first two years of life. We found that maternal dietary intake during pregnancy, and breast-feeding duration did not appear to influence the development of sensitisation to food allergens or FHS. Fruit and vegetable intake (≥ 5 portions per day) during pregnancy were however significantly associated with reduced FHS at age one and two. In addition fewer children whose mothers avoided a food, became sensitised or developed FHS to that particular food compared with those who did not. However as the numbers of children who were sensitised and/or had FHS were relatively small these findings cannot be regarded definitive and need to be explored further. As nearly half of the mothers reported avoiding peanuts, we also investigated the impact this may have had on their lives and that of their families. We interviewed mothers who had avoided peanuts as well as mothers who did not avoid peanut during pregnancy and breast-feeding. Emergent themes included: variations in information provision and the range of avoidance tactics adopted by participants; a lack of clarity in relation to information and advice about peanut avoidance, the risks entailed and the introduction of peanuts to the developing child’s diet; the importance of experience of atopy in influencing participants’ decisions to avoid peanuts and the importance of individuals’ choice in the decision making process. In this part of the project we concluded that improvements to the experience of avoidance and/or non-avoidance were primarily focused around provision of information and advice. In particular, a need for clear, consistent factual information and advice about the real risks associated with peanut consumption during pregnancy/lactation, and to whom these risks apply.
The project also addressed the question of whether there has been a change on sensitisation rate and symptomatic allergy to peanuts during the last decade or so. This was done by comparing the birth cohort born between 2001-2002 (post COT report) and reviewed at 3 years of age to two cohorts born prior to the publication of the COT report (a cohort of children born in 1989 and reviewed at 4 years of age, and a cohort born between 1994-1996 and reviewed at 3 years of age). With regards to changes in clinical allergy we compared the cohort born between 1994-1996 to the cohort born between 2001-2002. There was no significant change in the rate of peanut allergy between the cohorts (p=0.146, Fishers Exact Test).
The rate of sensitisation to peanuts for the two cohorts born prior to the publication of the COT reports was 1.1% and 3.3% respectively. This represented a significant increase in rates of sensitisation to peanut in this relatively short period. The rate of sensitisation to peanuts for the cohort born after the publication of the COT report was 2.0%. Analysing the trend over time revealed a statistically significant non-linear pattern with the peak occurring in the second cohort born between 1994-1996. It is tempting to postulate that the observed decline in sensitisation rate could be due to the impact of the COT recommendation. However, we feel the strength of this evidence is weak as the data is subject to a number of biases such as recall and accuracy bias on peanut consumption information obtained from the cohort born after the publication of the COT report. Additionally, we did not collect any information on peanut consumption during pregnancy and breast-feeding from the mothers of cohorts born prior to the publication of the COT report and a direct comparison cannot be made.
In conclusion this three-year project met all its objectives. The findings of this project resulted in four international presentations. Two peer-reviewed papers have already been published and a further two are being prepared.
- Main File
- T07034 Appendix 1
- T07034 Appendix 2
- T07034 Appendix 3
- T07034 Appendix 3a
- T07034 Appendix 3b
- T07034 Appendix 3c
- T07034 Appendix 4
- T07034 Appendix 5
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