Do short birth intervals have long-term implications for parental health? Results from analyses of Norwegian register data

Short inter-pregnancy intervals are associated with poorer birth outcomes and child survival. Adverse effects of short intervals for maternal outcomes have also been reported. Stresses arising from depleted nutrition or strains associated with raising two children close in age might be hypothesised to also have longer term effects on parental health. Such possible longer term implications have rarely been investigated but two UK studies suggest negative effects of short birth intervals for mortality and disability in later life. We investigate associations between inter-birth intervals and mortality risks in late middle age using high quality register data for the whole Norwegian population. Associations with use of prescription medication are also investigated. We focus on parents of two-four children and control for age, year of observation, education, marital status, age at first birth, parity and, in some models, change in co-parent since the previous birth. Results show negative effects of birth intervals of less than 18 months on mortality risks, and medication use, for mothers and fathers later in the life course and raised risks for mothers of twins. Results suggests the operation of biosocial pathways which, together with possible confounding via various selective influences, need further investigation.