Perceived health, fertility, and social network of middle-aged and older women in Japan

The fertility history of both women and men is associated with health and mortality in later life. The objective of this study was to analyze the associations between parity, social network, and perceived health measured using the Total Health Index (THI) consisting of 130 questions. The analytic sample included 4,858 women with a mean (SD) age of 54.4 (8.3) years who participated in the baseline study of the Komo-Ise cohort in 1993 and responded to the THI questionnaire. Data on parity were obtained from a follow-up study in 2000. THI scores differed across women with different parities. The mean (SD) of the integrated scale (T1) of THI calculated using a principal component analysis ranged between 0.3 (1.1) for nulliparous and -0.1 (1.0) for women of parity five or higher. A higher T1 reflected worse perceived health and predicted higher mortality in a previous study using the Komo-Ise cohort data. However, the association between parity and T1 became weaker and less consistent after adjusting for social network variables. The results suggest that the observed associations between parity and perceived health can be mediated by social support and networks. Causal relationships between parity, perceived health, and social networks need to be investigated in future research.