Association of Vitamin D status with acute respiratory infection and diarrhoea in children less than two years of age in an urban slum of Bangladesh

Ahmed, A. M. Shamsir (2016). Association of Vitamin D status with acute respiratory infection and diarrhoea in children less than two years of age in an urban slum of Bangladesh PhD Thesis, School of Public Health, The University of Queensland. doi:10.14264/uql.2016.640

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Author Ahmed, A. M. Shamsir
Thesis Title Association of Vitamin D status with acute respiratory infection and diarrhoea in children less than two years of age in an urban slum of Bangladesh
School, Centre or Institute School of Public Health
Institution The University of Queensland
DOI 10.14264/uql.2016.640
Publication date 2016-08-29
Thesis type PhD Thesis
Supervisor Abdullah Mamun
Ricardo Soares Magalhaes
Kurt Z. Long
Tahmeed Ahmed
Total pages 161
Language eng
Subjects 1111 Nutrition and Dietetics
1117 Public Health and Health Services
1103 Clinical Sciences
Formatted abstract
Background and aims: Diarrhoea and pneumonia are leading causes of morbidity and mortality in children under two years of age, and micronutrients have been shown to play an important role in the prevention of these conditions. The immune-modulatory functions of vitamin D in infectious diseases are well known; however, its role in childhood conditions such as diarrhoeal and acute respiratory infections (ARI) is limited and contradictory. Additionally, there are no studies reporting the role of vitamin D on pathogen specific diarrhoeal diseases.

I aimed to quantify the prevalence and identify the socioeconomic predictors of vitamin D status; evaluate the association of vitamin D status with diarrhoeal incidence and severity and whether vitamin D status confounded the association between other micronutrients and diarrhoeal incidence and severity; explore the role of vitamin D in diarrhoeal events with enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC) and enteroaggregative E. coli (EAEC); and investigate the association of vitamin D, retinol and zinc status with ARI in underweight and normal-weight children aged 6–24 months in urban slum of Bangladesh.

Methods: I analysed data from the Bangladeshi component of the Malnutrition & Enteric Diseases (Mal-ED) project, which is a multisite project concerned with malnutrition and diarrhoeal diseases in early childhood. As part of the Bangladeshi Mal-ED project, a prospective case-control study was conducted in children aged 6–24 months at the urban Mirpur field site in Dhaka. From November 2009 to February 2012, 500 cases and 480 controls were enrolled and matched for sex and area of residence. Cases were defined as children who were severely to moderately underweight (weight-for-age Z, WAZ, score < –2.00 SD) and controls were defined as well-nourished or normal-weight children (WAZ > –1.00). Serum vitamin D and other micronutrients were measured at baseline and children were followed for five months with active biweekly surveillance for common infectious diseases. Diarrhoeal stool samples were collected for isolation and characterisation of causative organisms. Data on household socio-economic status, and dietary intake were also collected. Data for underweight and normal-weight children were analysed separately. Multinomial logistic regression was used to identify risk indicators of vitamin D status. Multivariable generalised estimating equations (GEE) were used to estimate the incidence rate ratios of diarrhoea and ARI. Cox proportional hazard models of unordered failure events of the same type were used to determine risk factors for ETEC, EPEC and EAEC diarrhoeal incidence.

Results: Among underweight children only 23.1% were vitamin D sufficient (≥75 nmol/L), 42.3% insufficient (50-74.99 nmol/L) and 34.6% deficient (<50 nmol/L), In normal-weight children 14.8% were vitamin D sufficient, 39.6% insufficient and 45.6% were deficient. Risk factors [ORs (95% CIs)] for vitamin D deficiency in underweight children were: older age group (18–24 months) [2.9 (1.5–5.7)] compared to younger age group (6-11 months); measurement of vitamin D status during winter [3.0 (1.4–6.4)] and spring [6.9 (3.0–16.1)] compared to during summer; and maternal education (≥6 years of institutional education) [2.2 (1.0–4.9)] compared to illiterate mothers. Risk factors in normal-weight children were: older age group [3.6 (1.2–10.6)] and being from a household in the wealthiest quintile [3.7 (1.1–12.5)] compared to being from lowest quintile”.

Normal-weight and underweight children contributed 62,117 and 62,967 days observation, with 14.2 and 12.8 days/child/year of diarrhoea, respectively. None of the multivariable models (GEE) showed significant associations between vitamin D status and diarrhoeal morbidity. Zinc-insufficient normal-weight children had 1.3 times more days of diarrhoea and 1.8 times more risk of severe diarrhoea than zinc-sufficient children (p <0.05). Vitamin D status was not independently associated with the risk of ETEC, EPEC and EAEC diarrhoea in underweight children but moderate to severe retinol deficiency was associated with a reduced risk for EPEC diarrhoea. Among normal-weight children, insufficient vitamin D status and moderate to severe retinol deficiency were independently associated with 44% and 38% reduced risk of incidence of EAEC diarrhoea, respectively.

Underweight children with insufficient and deficient vitamin D status had 20% and 23–25% reduced risk of upper respiratory infection (URI) respectively compared with children with sufficient vitamin D status. Underweight children, with retinol deficiency, were at 1.8 (1.4–2.4) times higher risk of acute lower respiratory infection (ALRI) than those with retinol sufficiency. Normal-weight children with zinc insufficiency and those with retinol deficiency had 1.2 (1.0–1.5) times higher risk of URI and 1.9 (1.4–2.6) times higher risk of ALRI respectively.

Conclusion: These findings have important public health implications. Given the significant burden of vitamin D insufficiency and deficiency, intervention programs for accessing natural sources of vitamin D need to be prioritised urgently to prevent chronic diseases such as bone disease, diabetes mellitus, hypertension, and many common cancers during adulthood. My findings demonstrate that vitamin D did not confound the effect of zinc and vitamin A in childhood diarrhoea or ARI, and thus supplementation programs with vitamin D could be recommended for children under two years during winter and spring. However, findings also indicate that vitamin D induced immunomodulatory functions of innate and adaptive immunity in infectious disease morbidity warrants further exploration.
Keyword Diarrhoea
Acute respiratory infections
Vitamin D
Zinc
Retinol
Under two children
Undernutrition
Risk factors
Urban slum
Bangladesh

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Created: Wed, 17 Aug 2016, 03:58:22 EST by A M Shamsir Ahmed on behalf of Learning and Research Services (UQ Library)