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Vitamin D intake during the first 4 years and onset of asthma by age 5: A nested case‐control study
Author(s) -
Nwaru Bright I.,
Hadkhale Kishor,
Hämäläinen Niina,
Takkinen HannaMari,
Ahonen Suvi,
Ilonen Jorma,
Toppari Jorma,
Niemelä Onni,
Haapala AnnaMaija,
Veijola Riitta,
Knip Mikael,
Virtanen Suvi M.
Publication year - 2017
Publication title -
pediatric allergy and immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.269
H-Index - 89
eISSN - 1399-3038
pISSN - 0905-6157
DOI - 10.1111/pai.12773
Subject(s) - medicine , asthma , vitamin d and neurology , nested case control study , longitudinal study , pediatrics , population , allergy , vitamin , cohort study , cohort , case control study , confounding , environmental health , immunology , pathology
Abstract Background Early‐life vitamin D intake has been linked to asthma risk in childhood, but the role of longitudinal vitamin D exposure has not been previously evaluated. We investigated the association between vitamin D intake during the first 4 years of life and asthma risk by age 5. Methods Within a Finnish population‐based birth cohort, 182 incident asthma cases were matched to 728 controls on sex, genetic risk for type 1 diabetes, delivery hospital, and time of birth. Vitamin D intake was assessed by age‐specific 3 day food records. Parents completed a validated version of the International Study of Asthma and Allergies in Childhood questionnaire at 5 years. Results At 3 months, supplements were the main source of vitamin D intake; intake from foods increased from 3 months on, mainly from fortified milk products. Vitamin D intake at each specific age was associated with an increased risk of any asthma, atopic, and non‐atopic asthma, but only intake at 1 and 2 years was statistically significantly associated with asthma. Longitudinal vitamin D intake was associated with an increased risk of asthma ( OR 1.24; 95% CI 1.00‐1.53). Conclusions Increased vitamin D intake in childhood, particularly intake at 1 and 2 years of age, may increase risk of childhood asthma. This might reflect a true effect or residual confounding by lifestyle or environmental factors. Repeated assessment of vitamin D intake allowed evaluation of the longitudinal and age‐dependent impact of vitamin D on the risk of asthma. Further longitudinal studies are required to confirm or question these findings.