Survival Analysis to Determine the Significant Factors Associated with Birth Interval of Women in Ethiopia: Based on 2011 Ethiopian Demographic and Health Survey Data

Abstract

Longer intervals between consecutive births decrease the number of children a woman can have. This results in beneficial effects on population size and on the health status of mothers and children. The general objective of this study was to model the birth intervals of adult women age 15-49 years old in Ethiopia and to identify the variable that affects the length of birth intervals of women. The study utilizes the data extracted from the 2011 Ethiopian Demographic and Health Survey (EDHS). In this study cox proportional hazards and shared gamma frailty models were adopted for the analysis to identify important demographic and socioeconomic factors that may affect the length of birth intervals and to analyze correlated birth intervals respectively. The result of the two models revealed that mother’s age, place of residence, mother education level, wealth index, mother age at first birth, childbirth order, survival status of the previous child, breast feeding status, and contraceptive use were found to have significant effect on the length of birth interval for Ethiopian women. The analysis with the frailty model shows that child birth order may not be an important covariate for analyzing birth intervals, especially when mother’s age at first birth is already in the model. Moreover, shared gamma frailty model have resulted in a minimum AIC as compared to cox proportional hazard model without frailty term in the model, suggesting that shared gamma frailty model is the most powerful one in predicting the birth intervals of women among regional states of Ethiopia. Hence, the setting of correlated observations, the cox frailty models are recommended for providing statistically valid estimates of the effects of proximate determinants after adjusting for the background variables and unobserved random effects.