Food insecurity, vitamin D insufficiency and respiratory infections among Inuit children

1Division of Pediatric Respiratory Medicine, Department of Pediatrics, Sainte-Justine University Health Center, Montréal, Quebec, Canada; 2School of Dietetics and Human Nutrition, McGill University, Montreal, Quebec, Canada; 3Division of Pediatric Respirology, Department of Pediatrics, Children’s Hospital of Eastern Ontario, Ottawa, Quebec, Canada

Abstract

Background. Food insecurity, vitamin D deficiency and lower respiratory tract infections are highly prevalent conditions among Inuit children. However, the relationship between these conditions has not been examined in this population.

Objective. The objective of this study was to examine the relationship between food insecurity and severe respiratory infections before age 2 years and health centre visits for a respiratory problem in the past year. We also explored the relationship between serum vitamin D status and respiratory outcomes in this population.

Design. We included children aged 3–5 years who participated in a cross-sectional survey of the health of preschool Inuit children in Nunavut, Canada, from 2007 to 2008 (n=388). Parental reports of severe respiratory infections in the first 2 years of life and health care visits in the past 12 months were assessed through a questionnaire. Child and adult food security were assessed separately and serum 25-hydroxyvitamin D3 levels were measured in a subgroup of participants (n=279). Multivariate logistic regression was performed to assess the association between food security, vitamin D and each of the 2 respiratory outcomes.

Results. Child and adult food insecurity measures were not significantly associated with adverse respiratory outcomes. Household crowding [odds ratio (OR)=1.51, 95% confidence interval (CI) 1.09–2.09, p=0.01 for the child food security model] and higher birth weight (OR=1.21, 95% CI: 1.02–1.43, p=0.03) were associated with reported severe chest infections before age 2 years while increasing age was associated with decreased odds of reported health care visits for a respiratory problem (OR=0.66, 95% CI: 0.48–0.91, p=0.02). Neither vitamin D insufficiency nor deficiency was associated with these respiratory outcomes.

Conclusions. Using a large cross-sectional survey of Inuit children, we found that household crowding, but not food security or vitamin D levels, was associated with adverse respiratory outcomes. Further studies are warranted to examine the impact of decreasing household crowding on the respiratory health of these children.

Keywords: food security; vitamin D; Inuit; bronchiolitis; lower respiratory tract infections; crowding

Citation: Int J Circumpolar Health 2016, 75: 29954 – http://dx.doi.org/10.3402/ijch.v75.29954

Copyright: © 2016 Sze Man Tse et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 International License, allowing third parties to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material for any purpose, even commercially, provided the original work is properly cited and states its license.

Received: 5 October 2015; Revised: 4 December 2015; Accepted: 17 January 2016; Published: 15 February 2016

Competing interests and funding: The authors have not received any funding or benefits from industry or elsewhere to conduct this study.

*Correspondence to: Sze Man Tse, Division of Pediatric Respiratory Medicine, Department of Pediatrics, Sainte-Justine University Health Center, 3175 Chemin de la Côte-Sainte-Catherine, Montréal, Québec, Canada H3T 1C5, Email: sze.man.tse@umontreal.ca

To access the supplementary material for this article, please see Supplementary files under ‘Article Tools’

Canadian Inuit children have one of the highest rates of lower respiratory tract infections (LRTI) in the world, with admissions for LRTI being up to 10 times more frequent compared with other Canadian populations (1). Studies have documented an alarming hospitalization rate of 484 per 1,000 infants under 6 months of age for bronchiolitis (2). Rates of complications are also high, with 12.8% of admitted children requiring intubation (2). Bronchiolitis and pneumonia are clinically difficult to differentiate among children with LRTI. Among Inuit children, respiratory syncytial virus (RSV) has been identified as a common cause of LRTI (3). However, the rates of pneumonia, tuberculosis and post-infectious respiratory complications such as bronchiectasis are also substantially higher than in the rest of Canada (4). Despite the introduction of a 7-valent pneumococcal conjugate vaccine (PCV7) in 2002 and the 13-valent vaccine (PCV13) in 2010 in Northern Canada, pneumococcal pneumonia remains a major issue (5). Studies examining the effect of PCV7 in Northern communities have found that while there has been a decrease in invasive pneumococcal disease caused by serotypes included in the vaccine, there was an increase in disease caused by serotypes not included in PCV7 (6,7). A number of risk factors have been associated with respiratory disease prevalence and/or severity in Inuit children, including household overcrowding, passive and in utero smoke exposure, lack of breastfeeding and reduced ventilation in the house (8,9). Of these, household overcrowding and passive smoke exposure are highly prevalent.

Food insecurity is a prevalent problem among the Inuit, with nearly 70% of Inuit preschoolers residing in food insecure households (10). According to the 1996 World Food Summit, food security is achieved when “all people, at all times, have physical and economic access to sufficient, safe, and nutritious food to meet their dietary needs and food preferences for an active and healthy life” (11). Household food insecurity has been recognized as a determinant of childhood undernutrition (12) and other adverse health outcomes (13–15), including pneumonia (16), and nutritional deficiencies (17,18). Food insecurity has also been associated with childhood tuberculosis (19); however, the relationship between food insecurity and other respiratory infections is unclear.

Vitamin D deficiency is another highly prevalent problem among Inuit, due to their limited sun exposure in the winter (20) and inadequate dietary intake (21). Vitamin D deficiency has been associated with increased risk of respiratory infections in children (22,23). One trial found that supplementation with vitamin D was associated with a reduction in the risk of acute respiratory infections in Mongolian children (24). However, the biologic mechanisms underlying these associations have not been clearly elucidated. Despite the high prevalence of vitamin D deficiency among Inuit children, it is not known whether vitamin D deficiency is associated with respiratory infections in this population.

This study examined the relationship between food insecurity and adverse respiratory outcomes among Inuit children, namely reported severe respiratory infections before age 2 years and health centre visits for a respiratory problem. In addition, we explored the relationship between serum vitamin D status and respiratory outcomes in this population.

Methods

Subjects

Between the late summer and fall of 2007 and 2008, a cross-sectional survey of the health of preschool Inuit children was conducted in 16 communities of Nunavut, Canada. The details of this survey have been reported previously (10). Briefly, Inuit children aged 3–5 years from the surveyed communities were eligible to participate. They were recruited from community health centres’ lists of age-appropriate children and randomly selected households that had at least 1 participant in the International Polar Year Adult Inuit Health Survey for Nunavut. At the time of the survey, the total population of Inuit children aged 3–5 years in the 16 surveyed communities was 1,487, representing 77% of children in this age range in Nunavut. A total of 537 households were contacted, 75 of whom refused participation and 74 cancelled or failed to attend the study appointment. One child per household was selected to participate in the study. For households with 2 children or more in the target age range, the child whose birthday was closest to the date of the survey was selected to be the participant. Thus, 388 children were recruited into the study. Informed consent was obtained from the primary caregiver. The Nunavut Research Institute and the Institutional Review Board of the McGill Faculty of Medicine approved the study.
Ascertainment of food security and vitamin D status

Members of the research team conducted in-person interviews with primary caregivers in English or Inuit language or dialects. Food security was assessed using the 18-item Household Food Security Survey Module of the United States Department of Agriculture (25), with slight modifications by Indian and Northern Affairs Canada (26). Eight of these 18 questions are specific to food security status of children in the household and 10 are specific to adults. Food security status of the child and adult was determined using definitions established by Health Canada based on the number of affirmative responses on the questionnaire (27) and was divided into food secure, moderately food insecure and severely food insecure. Based on the presumption that adults may go hungry at the expense of providing food for their children, we examined the effect of child and adult food security on respiratory events separately. While both adult and child food insecurity affect children’s health, child food insecurity specifically has been associated with greater adverse health effects (28).

Blood was drawn from a subset of children (n=279) in the summer, as not all caregivers consented to the collection of a blood sample on their child. Plasma 25-hydroxyvitamin D3 concentrations, hereafter referred to as vitamin D, were measured using LIAISON total 25(OH)D at McGill University. Detailed methods for vitamin D measurement were reported previously (29). For the purpose of this study, vitamin D status was determined using the Canadian Pediatric Society guidelines (30), with vitamin D deficiency, insufficiency, and sufficiency defined as plasma levels Respiratory outcome measures

The in-person interview included the administration of demographic questionnaires and a questionnaire about respiratory illnesses and symptoms based on the standard ATS-DLD 78c questionnaire (31). The primary outcome consisted of the parental report of an episode of severe chest infection before age 2 years (“Did your child have a severe chest infection before s/he was 2 years old?”), which consisted of a report of bronchiolitis, pneumonia, and asthma. Asthma was included in this definition because it is typically triggered by a viral infection in this preschool age group. As a secondary outcome, we examined the parental report of health centre visits for a respiratory problem in the past 12 months (“In the last 12 months, did you ever have to take your child to the health centre/hospital for a cough, wheezing, or breathing problems?”). The prevalence of respiratory symptoms in this population has been reported previously (32).

Statistical analysis

We performed a descriptive analysis of general characteristics of the participants and multivariate logistic regression analysis to assess the association between food insecurity and each of the 2 respiratory outcomes. Age and sex were forced as obligatory covariates, while other covariates were included in the final model if they had a p-value of

A subgroup analysis was performed among the 279 participants who had a serum vitamin D level available. We performed multivariate logistic regression analysis to assess the association between vitamin D status and each of the 2 respiratory outcomes. Covariates include age, sex, body mass index (BMI) and the covariates included in the respective multivariate models for food security. p-Values are 2-sided. All analyses were performed using R, version 3.0.2 (www.r-project.org).

Results

General characteristics of the 388 children are presented in Table I, with stratification by respiratory outcomes presented in Supplementary Tables I and II. The mean age of this cohort was 3.9 (SD 0.8) years. The majority of these children had been breastfed (64.9%) and had been exposed to tobacco smoke in utero (81.4%) or passively in the house (89.4%). Most households were crowded [crowding is defined as more than 1 person per room (33)], with the median household crowding index at 3.0 people per room (IQR 1.5, 2.5). Summer serum vitamin D levels were available for 279 children, with a median of 48.4 nmol/L (IQR 33.1, 71.8), which is in the insufficient range according to the Canadian Pediatric Society (30).
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