Factors Influencing Initiation and Discontinuation of Vitamin D Supplementation Among Infants

: Background: To determine vitamin D supplementation frequency among infants, factors that influence adherence, and reasons for discontinuation of initiated vitamin D. Methods: This cross-sectional study was conducted using a questionnaire administered to the mothers via face to face interview on 560 infants aged from 1 to 24 months admitted to outpatient clinics from June to December 2017. Results: A total of 351 infants were administered vitamin D, and the rate of supplementation in the first year of life was 83%, while it was only 28% between 13 and 24 months. The rate of vitamin D supplementation was higher among infants who were exclusively formula-fed (p<.05). When the data were analyzed using logistic regression analysis, only visit family physicians seems to be a statistically significant independent variable in increasing supplementation (p<.05). Compared with family refusal, the rate of discontinuation of vitamin D by the healthcare providers was higher after the first year of life (p<.05). The rates of vitamin D discontinuation by healthcare providers, especially by nurses who considered the duration of supplementation adequate, was statistically significantly higher when compared with the fontanel closure and other reasons (p<0.05). Conclusions: The rate of vitamin D supplementation was higher among families who visited family physicians, which suggests the importance of well-baby visits. Since vitamin D supplementation was less common among exclusively breastfed infants, mothers should be educated. Healthcare professionals need further education about the importance of vitamin D supplementation and indications for discontinuation.

was 400 $ equivalent of Turkish Liras at the time of the study. Family incomes below this sum were defined as a low-income family. Monthly income, which was between the subsistence wages and up to two-fold of the subsistence wage, was defined as middle income. The income above this level was defined as high income. Infants were stratified into two groups based on their age; 1 to 12 months and 13 to 24 months. Twenty mothers who refused to complete the study questionnaire were excluded. No financial assistance was provided to participants. Interviews were recorded by one of the authors (SHK).

Statistical Analysis
Data obtained from the study was entered into the IBM SPSS Statistics Version 22.0 software. Chi-square test was used for univariate analysis. We further investigated the influence of different factors on the supplementation by multivariate logistic regression.
A p-value of less than 0.05 was considered to indicate a significant difference between groups. Data were expressed as numbers and percentages in tabulated form.

Results
Of a total of 560 infants participating in the study, 351 (62.6%) received vitamin D. The rate of supplementation during the first year of life was 83%, whereas it was only 28% between 13 to 24 months of life. There was no significant relation between infant's gender, delivery week, concomitant illnesses, medications, and vitamin D supplementation (p>.05, Table 1).
When compared by nutrition type, the rate of supplementation was higher among exclusively formula-fed infants. Vitamin D supplementation was initiated by family physicians in 264 (75.2%) and by pediatricians in 87 (24.8%) of the infants.
Supplementation rate was statistically significantly higher among families who regularly visited their family physicians and had their babies vaccinated on time (p<.05, Table 1). The rate of vitamin D supplementation among infants was higher in nuclear families than in crowded families (p<.05; Table 2). Supplementation rates were not associated with the presence of a sick child in the family, the number of children, household monthly income, paternal education and employment status, maternal age, education, and employment status (p>.05; Table 2). However, when the data were analyzed using logistic regression analysis, only visits to family physicians seem to be a statistically significant independent variable in increasing supplementation (p<.05; Table 3). Vitamin D was not administered to 209 (%37,3) infants. Compared with family refusal, the rate of discontinuation by the healthcare providers was higher after the first year of life. The rates of discontinuation by healthcare providers believing that the duration of supplementation was sufficient after the first year of life was significantly higher when compared with the fontanel closure and other reasons. Other reasons for discontinuation were kidney stones and the adequate vitamin D status of the infants.
Due to the belief insufficient duration of supplementation after the first year of life, nurses' discontinuation rates were high (p <.05; Table 4).

Conclusions
Since vitamin D supplementation rates were higher in families who visited their family physicians regularly, they must be encouraged to visit their family physician for well-baby visits at every opportunity. The newborn unit can be an ideal place to start a program that educates breastfeeding families about the need for supplements, as only breastfeeding infants receive less vitamin D. Healthcare providers has the most important role in supplementation practices, so they must participate in education programs on initiation and continuation of vitamin D supplements within the strategy of preventing vitamin D deficiency.
The limitation of this study is that it reflects regional results, so further studies at a national scale are required regarding supplementation practices. The low continuation rates of supplementation in our study, because of advice by healthcare providers, revealed the need for other studies to assess the knowledge and attitudes family of physicians and nurses directly by asking them.