Likely questionnaire-diagnosed food allergy in 78, 890 adults from the northern Netherlands

Abstract

Background: It is challenging to define likely food allergy (FA) in large populations which limited the number of large studies regarding risk factors for FA.

Objective: We studied the prevalence and characteristics of self-reported FA (s-rFA) in the large, population-based Dutch Lifelines cohort and identified associated risk factors.

Methods: Likely food allergic cases (LikelyFA) were classified based on questionnaire reported characteristics consistent with FA. Subjects with atypical characteristics were classified as Indeterminate. We investigated 13 potential risk factors for LikelyFA such as birth mode and living on a farm and addressed health-related quality of life (H-RQOL).

Results: Of the 78, 890 subjects, 12.1% had s-rFA of which 4.0% and 8.1% were classified as LikelyFA and Indeterminate, respectively. Younger age, female sex, asthma, eczema and nasal allergy increased the risk of LikelyFA (p-value range <1.00*10-250-1.29*10-7). Living in a small city/large village or suburb during childhood was associated with a higher risk of LikelyFA than living on a farm (p-value = 7.81*10-4 and p = 4.84*10-4, respectively). Subjects classified as Indeterminate more often reported depression and burn-out compared to those without FA (p-value = 1.46*10-4 and p = 8.39*10-13, respectively). No association was found with ethnicity, (duration of) breastfeeding, birth mode and reported eating disorder. Mental and physical component scores measuring H-RQOL were lower in both those classified as LikelyFA and Indeterminate compared to those without FA.

Conclusion: The prevalence of s-rFA among adults is considerable and one-third reports characteristics consistent with LikelyFA. Living on a farm decreased the risk of LikelyFA. The association of poorer H-RQOL as well as depression and burn-out with questionable self-perceived FA is striking and a priority for future study.

Fig 1. Flowchart of the study population and food allergy classification.

FAQ = Food Allergy Questionnaire. Q1 = question 1 (Which of the following food-items cause an allergic reaction?). NoFA = no food allergy, LikelyFA = likely food allergy. As indicated, only subjects who reported at least one food and at least one symptom consistent with immediate allergic reactions to food and who reported only likely characteristics of food allergy were classified as LikelyFA. All other cases who reported any food in Q1 were classified as Indeterminate. ^a n = 372 only reported a food which caused an allergic reaction, which is not described in S1 Table since it was reported in less than 1:1000 of patients with s-rFA. Furthermore, n = 312 only reported something other than a food such as ‘I don’t know’,’ currently under investigation’ or ‘not applicable’. ^b These unlikely characteristics are symptoms appearing after a day or more, following at least a normal portion or more, symptoms persisting for >1 week, a diagnosis by an alternative practitioner without a diagnosis by any clinician and a negative double-blind, placebo-controlled food challenge, see Table 1.

Fig 2. The prevalence of LikelyFA per age category and gender.

Being male and an older age were associated with a lower risk of FA (OR per year = 0.99, 95%CI = 0.99–1.00, p = 1.29*10^-7and OR for being female = 1.87, 95%CI = 1.72–2.03, p = 9.73*10⁻⁵⁰).

Fig 3. The prevalence of LikelyFA per answer as reported to the question ‘What is the best description of the place where you lived most of the time when you were younger than 5 years old?’.

^a OR = 1.39, 95%CI = 1.23-.58, p = 3.48*10−⁷, adjusted for age, gender, asthma, eczema and nasal allergy OR = 1.14, 95%CI = 0.99–1.30, p = 0.06. *^b OR = 1.73, 95%CI = 1.52–1.98, p = 4.52*10−¹⁶, adjusted for age, gender, asthma, eczema and nasal allergy OR = 1.27, 95%CI = 1.11–1.47, p = 7.81*10⁻⁴. *^c OR = 1.67, 95%CI = 1.43–1.95, p = 1.51*10−¹⁰, adjusted for age, gender, asthma, eczema and nasal allergy OR = 1.34, 95%CI = 1.14–1.57, p = 4.84*10⁻⁴. ^d OR = 1.356, 95%CI = 1.11–1.66, p = 0.04*10−¹, adjusted for age, gender, asthma, eczema and nasal allergy OR = 1.08, 95%CI = 0.88–1.34, p = 0.46.