Study design
This study used secondary data collected from the fourth round of the National Family Health Survey (NFHS-4), conducted in 2015–16. A cross-sectional study was designed.
Sample size and procedure
All living under-five children (n=247,743) who participated in the NFHS-4 were enrolled in the study. The NFHS-4 is a nationally representative large-scale sample survey carried out across all the states and union territories of India. The samples were selected using a two-stage stratified sampling design. In the first stage, the clusters were selected using the method of probability proportional to size. In the second stage, complete household mapping and listing have done in the selected clusters and 22 households were randomly selected from each cluster. The sampling frame used in this survey was the 2011 Indian Population and Housing Census. A detailed description of the sampling design and survey procedure is provided in the NFHS-4 national report [5].
Outcome variable
The outcome variable of this study is diarrhea in under-five children. Diarrhea is defined as having three or more loose or watery stools in 24 hours, as reported by the mother/caregiver in the past two weeks preceding the survey.
Explanatory variables
Socio-demographic and environmental characteristics were included for explanatory variables in this study. Socio-demographic characteristics include place of residence (rural and urban), caste (scheduled caste/scheduled tribe, other backward classes and others), religion (Hindu, Muslim and others), maternal education (illiterate/primary and secondary/above) father’s education (illiterate/primary and secondary/above), maternal age (15–24, 25–34 and 35–49 years), maternal body mass index [BMI] (underweight, normal and obese), access to mass media (no and yes), household size (<6 and 6+), wealth quintile (poorest, poorer, middle, richer and richest), region (north, central, east, northeast, west and south), age of child (0–11, 12–23, 24–35, 36–47 and 48–59 months), sex of child (male and female), birth order (1, 1–3 and 4+) and birth weight (<2.5 kg [low birth weight] and ≥2.5 kg [normal]).
Environmental characteristics include the availability of toilet facility, sources of drinking water, child stool disposal, and main floor and roof materials of the household. Household toilet facility was a dichotomous variable, classified as households having a toilet facility and households without a toilet facility. Any improved, unimproved and shared latrine facility (flush or pit) were considered as households having a toilet facility, otherwise households using open defecation. Sources of drinking water were categorized as improved and unimproved sources. Improved sources of drinking water are protected from outside contamination, particularly from fecal matter [22]. Improved sources include piped water, public taps, standpipes, tube wells and boreholes, protected dug wells and springs, rainwater, and community reverse osmosis plants, while unimproved sources comprise unprotected dug well, unprotected spring, tanker/cart with small tank, surface water and bottled water. Child stool disposal was grouped into safe and unsafe disposal. Child’s stool was considered to be safely disposed, if a child used a toilet or latrine, or flushed into a toilet, or it was buried [5]. The main floor materials of the houses were categorized as dirt (e.g., mud/clay/earth, sand and dung) and non-dirt (e.g., raw wood planks, palm, bamboo, brick, stone, parquet or polished wood, vinyl or asphalt, ceramic tiles, cement, carpet and polished stone/marble/granite). Likewise, the main roof materials of the dwelling unit were grouped into thatch (e.g., thatch/palm leaf, mud, plastic/polythene, rustic mat, palm/bamboo, timber etc.) and metal/concrete (e.g., metal, wood, asbestos sheets, cement/concrete, tiles, slates, burnt bricks etc.).
Data analysis
Descriptive statistics were carried out to understand the distribution of socio-demographic and environmental characteristics for the study sample. The prevalence of diarrheal disease was estimated by selected explanatory variables. Pearson’s chi-square test was used and variables with p<0.05 were included for further analysis. The sample weight was used for the estimation of percentage distribution. Bivariate and multivariate logistic regression models were employed to assess the socio-demographic and environmental factors associated with diarrhea in children under five. The regression results are presented by unadjusted and adjusted odds ratio (OR) with 95% confidence interval (CI) and the results were considered to be statistically significant at p<0.05. All the statistical analyses were performed using STATA version 14.0 (StataCorp LP, College Station, TX, USA).