RRTIs are one of the most prevalent reasons for children to attend clinics, be admitted to a hospital, and have antibiotics prescribed globally [1]. Recurrent infections in children frequently lead to repeated cases of cough, fever, sore throat, otitis media, bronchitis, and pneumonia, and are associated with poor school attendance, increased health care costs, and stunted growth. Respiratory tract infections are still a significant cause of childhood morbidity in developing countries, including Pakistan, which are associated with malnutrition, overcrowding, poor sanitation, and delayed health-care access. Recurrent infections are caused by several different factors, but there has been a growing body of evidence that vitamin D deficiency may play an important role in children's impaired immune defense mechanisms [2,3]. Vitamin D is a fat-soluble vitamin that plays a crucial role in calcium metabolism, bone growth, and maintenance of bone integrity [4]. Vitamin D is also known to possess several classical roles, and its immunomodulatory properties are central in the innate and adaptive immune system. Vitamin D receptors have been found in macrophages, dendritic cells, and lymphocytes, suggesting a role in immune regulation. Antimicrobial peptides such as cathelicidins and defensins are produced in adequate vitamin D levels and promote the defense of the respiratory mucosa against viruses and bacteria. Thus, Vitamin D deficiency can be a risk factor for recurrent respiratory tract infections [5,6]. Vitamin D deficiency is a problem of public health in the world today, present both in developed and developing nations. Although South Asian countries have an ample amount of sunlight, vitamin D deficiency is very common because people live indoors, lack appropriate food intake, have poor nutritional status, and have dark skin pigmentation, and their exposure to the sun is very limited. Researchers have found that children with low levels of vitamin D are more likely to have recurrent upper respiratory tract infections, asthma attacks, and to be sicker for longer [7]. Additionally, hypovitaminosis D and socioeconomic deprivation could exacerbate malnutrition and lead to recurrent infections [8]. Vitamin D deficiency in children has been reported to be prevalent in several regions in Pakistan. However, few local studies have focused on its association with recurrent respiratory tract infections and risk factors for them. Understanding of the modifiable factors, like poor sunlight exposure, poor nutrition, exclusive breastfeeding without supplementation, and low socioeconomic status, could also help design strategies to reduce pediatric respiratory morbidity. Avoiding vitamin D deficiency may make children more resistant to infection and enhance immune function when it is caught and treated early [9].The present study was conducted to find the prevalence of vitamin D deficiency in children attending a tertiary care hospital with recurrent respiratory tract infections, and to identify the associated risk factors in this setting, where recurrent respiratory tract infections are becoming a common problem, and the prevalence of vitamin D deficiency is high in children [10].

Study Objectives

To assess the prevalence of vitamin D deficiency and to assess vitamin D deficiency risk factors in children with recurrent respiratory tract infections (RTI) in a tertiary care hospital

Study Design & Setting A cross-sectional study was carried out in the Department of Pediatrics Unit II, Sandeman Provincial Hospital (SPH), Quetta, Pakistan, between July 2025 and Dec 2025. Participants The number of children enrolled in the study was 100 children aged 1-12 years with recurrent respiratory tract infections (RRTI), selected by a non-probability consecutive sampling technique. Evaluation was done on children visiting outpatient and inpatient pediatric services. Demographic information, nutritional history, feeding practices, sun exposure, and socioeconomic status were obtained with parents/guardians' informed consent from a structured proforma. Sample Size Calculation The sample size of 100 children was determined using the WHO sample size calculator with an expected prevalence of Vitamin D deficiency of 65%, the 95% confidence level, and a margin of error of 9%. There was sufficient statistical power in the calculated sample to identify the frequency and related risk factors. Inclusion Criteria • Children aged 1–12 years • Both male and female children • Children with recurrent respiratory tract infections (RRTIs) • The informed consent of parents/guardians Exclusion Criteria • Children who have been taking vitamin D in the last 3 months. • Chronic kidney disease, chronic liver disease, congenital heart disease, or malabsorption syndromes in children • Immunocompromised children • Other children who have a bone condition due to genetic or metabolic factors. Diagnostic and Management Strategy All children had a detailed clinical history and physical examination. Laboratory assays were used to determine serum vitamin D levels. Vitamin D deficiency was defined as serum levels < 20 ng/mL, and deficiencies were treated according to standard pediatric vitamin D supplementation and nutritional counseling. Statistical Analysis The collected data were entered and analyzed in SPSS version 26. Data for quantitative variables were summarized as mean ± SD, and data for qualitative variables were reported as frequencies and percentages. Chi-square test was used for the association between vitamin D deficiency and risk factors. A p-value ≤0.05 was considered statistically significant

A total of 100 children with recurrent respiratory tract infections were included in the study. Among them, 58 (58%) were males and 42 (42%) were females. The mean age of participants was 5.8 ± 2.7 years. Vitamin D deficiency was detected in 68 (68%) children, while 20 (20%) had insufficient vitamin D levels and only 12 (12%) had normal levels. Children with inadequate sunlight exposure demonstrated a significantly higher prevalence of vitamin D deficiency compared to those with adequate exposure (78% vs 42%; p=0.002). Malnutrition was also significantly associated with deficiency, as 74% of malnourished children had low vitamin D levels compared to 46% among well-nourished children (p=0.01). Exclusive breastfeeding without vitamin D supplementation beyond six months showed a statistically significant association with deficiency (p=0.03). However, no significant relationship was observed between gender and vitamin D deficiency (p=0.41). The mean serum vitamin D level among deficient children was 14.2 ± 3.8 ng/milk Children experiencing severe recurrent respiratory tract infections had significantly lower vitamin D levels compared to children with mild infections (12.9 ± 3.1 ng/mL versus 18.4 ± 4.2 ng/mL; p=0.001), indicating a strong association between hypovitaminosis D and infection severity.

Table 1: Demographic Characteristics of Study Participants (n=100)

Table 1 demonstrates the demographic profile of enrolled children presenting with recurrent respiratory tract infections. Most participants were male, and the majority belonged to low socioeconomic families.

Table 2: Frequency of Vitamin D Status Among Children (n=100)

Table 2 shows the distribution of serum vitamin D levels among study participants. Vitamin D deficiency was highly prevalent, affecting more than two-thirds of enrolled children.

Table 3: Association of Risk Factors with Vitamin D Deficiency

Table 3 presents the association between various risk factors and vitamin D deficiency. Inadequate sunlight exposure, malnutrition, and lack of vitamin D supplementation showed statistically significant associations with deficiency.

Table 4: Relationship Between Severity of Respiratory Infections and Vitamin D Levels

Table 4 compares serum vitamin D levels according to severity of recurrent respiratory tract infections. Children with severe infections had significantly lower vitamin D levels compared to those with mild infections.

The Finding indicated that vitamin D deficiency was significantly high, with 68% of the enrolled children suffering from it. Lack of vitamin D supplementation, low sun exposure, and malnutrition were also deemed to be significant risk factors. Children who had severe recurrent infections also had significantly lower vitamin D levels in their blood. The results are consistent with the increasing evidence surrounding the role of vitamin D as an immunomodulator in the health of the respiratory tract in children [11]. This study's level of vitamin D deficiency is similar to that of other recent regional and international studies. In a study by Ahmed et al. 64% of children with recurrent respiratory infections were reported to be vitamin D deficient, and Khan et al. reported vitamin D deficiency in 71% of hospitalized children. In parallel, the Indian and Bangladesh studies also showed that 60% to 75% of the children with recurrent upper and lower respiratory tract infections were found deficient in this study [12]. The similarities are likely due to similar socio-economic conditions, dietary deficiencies, overcrowding, and insufficient knowledge about appropriate vitamin D consumption among South Asian populations [13]. In the current study, low sun exposure was statistically significant (p=0.002) as a risk factor for vitamin D deficiency. This is in line with a recent study, which reported that children with reduced outdoor exposure activities, excessive indoor lifestyle, and environmental pollution were associated with decreased vitamin D synthesis in skin [14]. Sun exposure is limited in developing countries due to cultural factors, urban settings, and extended indoor education. In the same way, a multicenter study of the pediatric population done in 2023 showed that children who spent less than 30 minutes in the sun per day had significantly higher odds of hypovitaminosis D [15]. Another important factor in the present study associated with vitamin D deficiency was malnutrition (p=0.01). This result corroborates earlier studies showing that nutrient deficiencies in children have adverse effects on their micronutrient status and immune system [16]. Nutritional deficiencies can also be exacerbated by poor dietary practices, low intake of fortified foods, and frequent illnesses. The close relationship between nutritional status and immune competence was further highlighted by Hussain et al. who reported significantly reduced serum vitamin D levels in malnourished children with recurrent pneumonia [17]. The levels of deficiency were statistically significantly related to exclusive breastfeeding without vitamin D supplementation past six months (p=0.03). Recent pediatric studies have found similar results, with one study focusing on the fact that vitamin D levels in breast milk alone are not high enough to meet infant vitamin D needs unless the mother has adequate levels [18]. Vitamin D supplementation is thus recommended in infants to prevent vitamin D deficiency and to help maintain immune system function, based on international recommendations. One key result from this study was the link between lower levels of serum vitamin D and higher respiratory tract infection (RTI) severity. The vitamin D level was significantly low in children with severe recurrent infections as compared to those with milder disease (p = 0.001). Similar findings were described by recent meta-analysis and cohort studies that found vitamin D deficiency is linked to increased susceptibility to viral respiratory infections, length of hospital stay, and severity of respiratory disease [19]. Vitamin D promotes innate immunity via upregulation of antimicrobial peptide production and regulation of inflammation, which lessens the vulnerability of the respiratory mucosa to pathogens [20]. The findings of this study have important clinical implications. Vitamin D deficiency can be screened for early in children with recurrent respiratory tract infections, which can help to provide timely interventions and supplementation. Seeking nutrition advice, promoting outdoor physical activity, and educating children about adequate sunlight exposure can help lower the burden of recurrent infections in children [21]. But there were some shortcomings in this study. It was a single-center study, with a small number of children involved, so the results are not necessarily generalizable. Vitamin D was not assessed in-depth for seasonal fluctuations in levels and food consumption. Further multicenter longitudinal studies are recommended to confirm the causal association and the long-term effects of using vitamin D supplementation to prevent RRT in children. Limitations The study was done in one tertiary care center with a small sample size and might not be generalizable. The seasonal variability of vitamin D blood levels and dietary intake was not evaluated, nor were the long-term effects of supplementation. Larger multicenter longitudinal studies are recommended for more robust evidence,

Vitamin D deficiency was very common in RRTI children and was significantly related to low sunlight exposure and low levels of both nutrition and supplementation. In susceptible children, early diagnosis, nutritional advice, and vitamin D supplementation could have a positive effect on the severity of infection and subsequently the respiratory health outcomes for children.

Disclaimer: Nil

Conflict of Interest: Nil

Funding Disclosure: Nil

Authors Contributions

Concept & Design of Study:Shaista Saeed1,Mavia Nisar Achakzai2

Drafting:Fahad Iqbal3, Hina Mohammad Ali4

Data Collection & Data Analysis:Najeem Shah5

Critical Review: Shakila Asmat6

Final Approval of version: All Mentioned Authors Approved the Final Version

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