The Link Between Plasma 25-Hydroxyvitamin D and Lung Function in General and Asthmatic Children

Vitamin D and asthma occurrence in children: A systematic review and meta-analysis

PROBLEM

The association between serum 25-Hydroxyvitamin D (25-OHD) level and asthma occurrence in children was controversial.

ELIGIBILITY CRITERIA

The Pubmed, Ovid Medline, Embase, Cochrane Library were systematically searched up to April 13th 2020. All the study measured the serum 25-OHD level in children, or classified the children based on the 25-OHD level into severe vitamin D deficiency, insufficient deficiency and comparing the prevalence of asthma in childhood were included in our study.

SAMPLE

A total of 35 studies were included in our meta-analysis. Among them, 24 studies were included for analyzing the association between 25-OHD level and asthma, and 12 studies evaluated the treatment effect of vitamin D.

RESULTS

The children with asthma (5711 participants) had significant lower 25-OHD level than children without asthma (21,561 participants) (21.7 ng/ml versus 26.5 ng/ml, SMD = -1.36, 95% = -2.40--0.32, P = 0.010). Besides, the children with asthma treated with vitamin D supplement had a significantly lower recurrence rate than the placebo group (18.4% versus 35.9%, RR = 0.35, 95%CI = 0.35-0.79, P = 0.002).

CONCLUSIONS

Children with asthma had a lower 25-OHD level than healthy children. Vitamin D supplement could decrease the asthma recurrence rate in the follow-up years.

IMPLICATIONS

This study implies that lower 25-OHD may cause asthma in childhood.

Vitamin D Insufficiency and Asthma in a US Nationwide Study

BACKGROUND

Vitamin D insufficiency (a serum 25-hydroxy vitamin D level of <30 ng/mL) has been associated with asthma morbidity.

OBJECTIVE

To examine vitamin D insufficiency, asthma, and lung function among US children and adults.

METHODS

Using data from the National Health and Nutrition Examination Survey from 2001 to 2010, we examined vitamin D insufficiency and (1) current asthma or wheeze in 10,860 children (6-17 years) and 24,115 adults (18-79 years) and (2) lung function in a subset of participants. Logistic or linear regression was used for the multivariable analysis, adjusting for age, sex, race/ethnicity, income, body mass index, smoking, and C-reactive protein level.

RESULTS

Vitamin D insufficiency was associated with current asthma (odds ratio, 1.35; 95% CI, 1.11-1.64) and current wheeze in children, as well as with current wheeze in adults (odds ratio, 1.17; 95% CI, 1.04-1.31). After stratifying the analysis by race/ethnicity and (in adults) current smoking, vitamin D insufficiency was associated with current asthma and wheeze in non-Hispanic white children only; in adults, vitamin D insufficiency was associated with current wheeze in non-Hispanic whites and blacks. Vitamin D insufficiency was also associated with lower FEV1 and forced vital capacity in children and adults. When analyzing each National Health and Nutrition Examination Survey wave separately, vitamin D insufficiency prevalence was 72% to 76% from 2001 to 2006, and then decreased from 2007 to 2010 (64%-65%); interestingly, asthma prevalence decreased for the first time from the period 2007 to 2008 (8.2%) to the period 2009 to 2010 (7.4%).

CONCLUSIONS

We show racial/ethnic-specific associations between vitamin D insufficiency and current asthma or wheeze in children and adults. Moreover, we report parallel recent decrements in the prevalence of vitamin D insufficiency and asthma.

Serum 25-hydroxyvitamin D levels and lung function in adults with asthma: the HUNT Study

The association between vitamin D status and lung function in adults with asthma remains unclear. We studied this cross-sectional association and possible modification by sex and allergic rhinitis in 760 adults (aged 19-55 years) with self-reported asthma in the Nord-Trøndelag Health Study. Serum 25-hydroxyvitamin D (25(OH)D) level <50 nmol·L(-1) was considered deficient. Lung function measurements included forced expiratory volume in 1 s (FEV1) % predicted, forced vital capacity (FVC) % predicted and FEV1/FVC ratio. Multiple linear regression models were used to estimate adjusted regression coefficients (β) and 95% confidence intervals. 44% of asthma adults had serum 25(OH)D levels <50 nmol·L(-1). Its associations with lung function measures seemed to be modified by sex and allergic rhinitis (p<0.03 for three-way interaction term). Overall, a serum 25(OH)D level <50 nmol·L(-1) was not associated with lung function measurements in subjects with allergic rhinitis in this asthma cohort. In men with asthma but without allergic rhinitis, however, a serum 25(OH)D level <50 nmol·L(-1) was significantly associated with lower FEV1/FVC ratio (β=-8.60%; 95% CI: -16.95%- -0.25%). Low serum 25(OH)D level was not associated with airway obstruction in most asthma adults with the exception of men with asthma but without allergic rhinitis.