1. Introduction
deaths
The national economic growth in low- and middle- income countries (LMICs) has been rapidly developing for decades, potentially resulting in the improvement of child health. According to country-level data, the global under-five mortality rate substantially decreased by 53%, from 90.6 in 1990 to 42.5 deaths per 1,000 livebirths in 2015 (These discrepancies may be explained by the single-time point measurement of household wealth and cross-sectional nature of demographic and health surveys among these studies, which are unable to capture the mobility of individual household wealth. We only noted two studies conducted in high-income countries that measured socioeconomic status (SES) at multiple-time points, which, however, manually categorized the sample into subgroups by merging the low-, medium-, and high-SES at single-time point in an un-nuanced manner. They both reported that upward shift of household SES from baseline had benefits on later cardiovascular health (In this study, we used data from a birth cohort in rural western China where national economy has been rapidly developing for decades. In our village setting, individual families have wider range and higher diversities of household wealth as compared to those in eastern metropolitan cities in last decade, i.e., during our study period, providing the unique opportunity to assess the household wealth mobility. We prospectively followed participants at birth, mid-childhood (7–9 y) and early adolescence (10–14 y) and repeatedly assessed household wealth at each visit. We aimed to examine the associations of household wealth at single-time point, conditional increase between two single-time points and life-course relative mobilities (trajectories) from pregnancy to early adolescence with adolescent multiple health outcomes, including physical growth, cognitive development, and emotional and behavioral problems.