We enrolled 108 cases and 41 controls. The mean age of presentation was 2.18 ± 0.77 years for cases and 1.82 ± 0.62 years for controls. The youngest included child was one-year old. Children had fairly even distribution across various age groups; larger distribution was mainly in the age group between 2 years and 3 years. There was significant gender inequality in both the case and the control groups. There were 88 (81.4%) males and 20 (18.6%) females who fulfilled the criteria of recurrent wheezing. Among controls, there were 28 (68.3%) males and 13(31.7%) females. The male: female ratio of children with recurrent wheezing was 4.4:1. Among the study group 69 (63.8%) patients were from urban area and 39 (36.1%) of patients were from rural area. In the control group 34 (82.9%) were from urban area and 7 (17.1%) were from rural area. We calculated the serum levels of 25(OH) vitamin D of all the 108 cases and 41 controls. The mean levels of vitamin D in the cases and the controls were 16.08 ng/ml ± 14.9 and 23.37 ng/ml ± 17.9 respectively. The minimum and maximum levels of Vitamin D in the cases were 1.5 ng/ml and 36.75 ng/ml respectively. The minimum and maximum values in the controls group were 1.5 ng/ml and 70 ng/ml. The difference in vitamin D levels in the two groups was not statistically significant (p = 0.0619).
We further categorized the vitamin D levels of both the groups into deficient (< 20 ng/ml), insufficient (20–30 ng/ml) and sufficient (> 30 ng/ml). Among the cases 66 (61.1%) were deficient, 20 (18.5%) were insufficient, 22 (20.3%%) were sufficient. On the other hand, 24 (58.5%), 4 (9.8%) and 13 (31.7%) of the control population were deficient, insufficient and sufficient respectively.
In our study 91 (84%) cases were categorized as severe wheezers and 17 (16%) as non-severe. Among the Severe cases 57 (62.6%), 16 (17.5%) and 18 (19.7%) were vitamin D deficient, insufficient and sufficient respectively. In the non-severe group 9 (53%), 4 (23.5%) and 4 (23.5%) were vitamin D deficient, insufficient and sufficient respectively.
During enrolment, 13 cases showed features of pneumonia in chest Xray. We compared the vitamin D levels of these above children with the rest of the cases and found no statistically significant difference (p = 0.949 and likelihood ratio is .947).
We made an approximate estimate about exposure to sunlight. At least 15 min daily exposure was taken as adequate, although we didn’t confirm the area of exposure and time of the day. In our study 39 (39%) cases and 12 (29.27%) controls gave history of at least 15 min daily exposure to sunlight. The difference in exposure to sunlight among the cases and controls was not significant (p = 0.27). In our study, we found no difference in the serum vitamin D levels between adequately and inadequately sun exposed children. (p = 0.379).
A weak negative correlation was found between the vitamin D levels and frequency of wheezing in the last one year(r=-0.118), though not statistically significant (p = 0.22).
There was no significant difference in vitamin D levels between, urban and rural population (p = 0.612), among different socio-economic group (p = 0.77), vegetarians and non-vegetarians (p = 0.6).
We calculated the asthma predictive index of all our cases by specific pre-set questionnaires. In our study group 55 (51.0%) cases were API stringent index positive and 53 (49.0%) children were negative. The mean Vitamin D levels of API stringent Index positive and negative cases were 15.53 ± 10.52 ng/ml and 16.56 ± 11.9 ng/ml respectively.