25-hydroxy vitamin D levels are associated with childhood asthma in a population-based study in Peru

Abstract

Background: Vitamin D deficiency may be associated with an increased risk of asthma.

Objective: We studied the association between 25-hydroxy (25-OH) vitamin D deficiency and asthma prevalence in two Peruvian populations close to the equator but with disparate degrees of urbanization.

Methods: We conducted a population-based study in 1441 children in two communities in Peru, of which 1134 (79%) provided a blood sample for 25-OH vitamin D analysis.

Results: In these 1134 children, mean age was 14.8 years; 52% were boys; asthma and atopy prevalence was 12% in Lima vs. 3% in Tumbes (P < 0.001) and 59% in Lima vs. 41% in Tumbes (P < 0.001), respectively; and, mean 25-OH vitamin D level was 20.8 ng/mL in Lima vs. 30.1 ng/mL in Tumbes (P < 0.001). Prevalence of 25-OH vitamin D deficiency (< 20 ng/mL) was 47% in Lima vs. 7% in Tumbes (P < 0.001). In multi-variable logistic regression, we found that lower 25-OH vitamin D levels were associated with an increased odds of asthma (OR = 1.7 per each 10 ng/mL decrease in 25-OH vitamin D levels, 95% CI 1.2-2.6; P < 0.01). In stratified analyses, the association between lower 25-OH vitamin D levels and asthma was limited to children with atopy (OR = 2.2, 95% CI 1.3-3.6) and not in those without atopy (OR = 0.9, 95% CI 0.5-2.0). We did not find associations between 25-OH vitamin D levels and other clinical biomarkers for asthma, including exhaled nitric oxide, total serum IgE and pulmonary function.

Conclusion and clinical relevance: Both asthma and 25-OH vitamin D deficiency were common among children living in Lima (latitude = 12.0 °S) but not among those in Tumbes (3.6 °S). The relationship between 25-OH vitamin D deficiency and asthma was similar in both sites and was limited among children with atopy. Future supplementation trials may need to consider stratification by atopy at the time of design.

Keywords: Peru; asthma; childhood; vitamin D.

Figure 1

Flow diagram of recruitment, questionnaires and procedures in Lima and Tumbes, Peru; 2009 –2010.

Figure 2. Box-percentile plots of the distribution of serum 25-OH vitamin D levels in two Peruvian populations; 2009–2010

We display the distribution and percentiles (5%, 10%, 25%, 50%, 75%, 90%, 95%) of serum vitamin D levels stratified by study site.

Figure 3. Relationship between serum 25-OH vitamin D levels and asthma prevalence in two Peruvian populations; 2009–2010

Left panel displays a barplot to describe the relationship between asthma prevalence and quartiles of vitamin D levels in the entire cohort. The right panel displays asthma prevalence by quartiles vitamin D levels stratified by site (Lima in red, Tumbes in blue).

Figure 4. Relationship between serum 25-OH vitamin D levels and exhaled nitric oxide levels in two Peruvian populations; 2009–2010

Left panel displays a barplot to describe the relationship between exhaled nitric oxide and quartiles of vitamin D levels in the entire cohort. The right panel displays exhaled nitric oxide by quartiles vitamin D levels stratified by site (Lima in red, Tumbes in blue).

Figure 5. Relationship between serum 25-OH vitamin D levels and total serum IgE in two Peruvian populations; 2009–2010

Left panel displays a barplot to describe the relationship between total serum IgE and quartiles of vitamin D levels in the entire cohort. The right panel displays exhaled total serum IgE by quartiles vitamin D levels stratified by site (Lima in red, Tumbes in blue).