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Impact of the vitamin D deficiency on COVID-19 infection and mortality in Asian countries.
Take Home Message
The number of COVID-19 infections and mortalities per 1 M population were significantly associated with reported vitamin D deficiency levels and the association improved once factors such as median age of the population, prevalence of obesity and prevalence of diabetes mellitus were included in the analysis.
This population study investigated the association of prevalence of vitamin D deficiency and mean vitamin D level with COVID-19 infection and mortality in Asia.
- A total of 24 countries, satisfying the inclusion/exclusion criteria were selected for the analysis. Study population size varied, from 107 (Japan) to 142,131 (Lebanon). All studies included both men and women participants >18 years with some limited to adults <65 years. VDD was reported for all countries but mean VD level was only reported for 15 countries.
- In three-fourths of the countries, more than 50% of the adult population was VDD, with the lowest reported in Vietnam (2.0%) and the highest reported in Oman (87.5%). Mean vitamin D levels in Oman were the lowest (32.5 nmol/l) and the highest was in Vietnam (83.8 nmol/l).
- As of December 31, 2020, Vietnam reported the lowest COVID-19 infection rate with 15 cases/1 M while Bahrain had the highest with 53,679 cases/1 M.
- In the case of COVID-19 mortalities, Vietnam documented the lowest number at 0.4 deaths/1 M whereas the highest number, 655 deaths/1 M occurred in Iran.
- All western Asian countries (e.g., Qatar, Lebanon and Kuwait) reported higher values for both COVID-19 infections and mortalities compared to south-eastern Asian countries (e.g., Vietnam, Singapore and Brunei).
- Median age of the population is in the thirties across more than half of the countries, with Japan as the outlier with a median age of 48.6 years.
- The prevalence of diabetes mellitus across the 24 countries was similar at approximately 10%.
- Obesity had a wide prevalence range with the highest value of 35% in Bahrain and the lowest of 2% in Vietnam.
- The number of COVID-19 infections and mortalities per 1 M population were significantly positively correlated with VDD and the correlation improved once factors such as median age of the population, prevalence of obesity and prevalence of diabetes mellitus were included in the multiple regression analysis.
- Mean VD levels alone did not result in significant negative correlation with COVID-19 infections and mortalities but once other confounding factors were included in the analysis, significant correlations were achieved. A growing body of evidence connects obesity with COVID-19 as mean VD levels alone are not important but with adiposity the circulatory mean VD levels may change. Low mean VD is one of the metabolic disturbances associated with excess adiposity.
This study extracted the population data of 24 Asian countries for COVID-19 infection rates, deaths per 1 million citizens, vitamin D (VD) levels and vitamin D deficiency (VDD) rates for adults > 18 years.
Things to Keep in Mind
- All values used in this study are historical and may not represent the current vitamin D status, anthropometric measurements or comorbidities found in each country.
- The VDD and mean VD values included from published studies report values measured within a certain date range, which may not provide an accurate annual picture of a populations’ VD status as most countries have seasonal variations in vitamin D levels.
- Older adults (>65 years) were not included in all studies, but this population is at high-risk for COVID-19 morbidity and mortality.
- Obesity and diabetes mellitus prevalence data were extracted from WHO databases and may be outdated. Ideally, prevalence data for each country would be more precise if searched for each country individually. Obesity cut off values may differ from this database (BMI<30 kgm2) when focused on Asia as the cut off value would be lower due to a different body composition.
Prevalence of vitamin D deficiency is significantly positively associated whereas the mean vitamin D level is significantly negatively associated with both infection and mortality rate of COVID-19 among Asian countries upon predicting with all confounders.
- This population study investigated the association of prevalence of vitamin D deficiency (VDD) and mean vitamin D (VD) level with COVID-19 infection and mortality in Asia.
- Real time numerical data on COVID-19 infections and mortalities among Asian countries, as of December 31, 2020, were retrieved from the Worldometer website, for countries that had conducted a minimum of 10,000 PCR tests per one million (1 M) of the country’s population.
- A comprehensive electronic search was performed using both PubMed and Google Scholar to retrieve the information on the prevalence of vitamin D deficiency (VDD) among the selected countries.
- The search was limited to articles published in the last ten years with data for the adult population (>18 years). The resulting articles were screened based on the following inclusion criteria: a) Population-based studies; b) studies reporting noninstitutional adults; c) studies defining VDD as the serum concentration of 25(OH)D < 20 ng/ml or <50 nmol/l; d) studies reporting VDD as the prevalence of the sample population.
- Out of the screened articles for each country, the most recently published study, with the most representative sample of each country was selected for extracting data
- The data on the prevalence of obesity (BMI ³30 kg/m2) and diabetes mellitus (fasting glucose ³0 mmol/l) were extracted from non-communicable disease (NCD) country profiles published by the Non-communicable Diseases and Mental Health Cluster (NMH) of the World Health Organization.
- The median age of each country’s population was retrieved from the World Fact Book of the Central Intelligence Agency (CIA), which constitutes basic information on sociodemographic factors of 266 world entities.