The influence of socioeconomic status on the association between residential greenness and gestational diabetes mellitus in an urban setting: a multicenter study.

BACKGROUND

Inconsistencies were found between residential greenness and the risk of gestational diabetes mellitus (GDM), possibly due to variations in susceptibility among populations with different characteristics. However, little is known about whether this association could be modified by population characteristics like socioeconomic status (SES). This multicenter study conducted in a dense megacity aims to clarify these associations and explore the modification effects of demographic and socioeconomic factors.

METHODS

The study included 19,618 pregnant women in 20 hospitals throughout Shanghai, China, between 2015 and 2017. Multivariable logistic regression models were utilized to assess the associations of satellite-based greenness indicators [normalized difference vegetation index (NDVI) within 500 m- and 1000 m buffers] with GDM and whether demographic and socioeconomic factors modified the associations. Potential mediation effects of fine particulate matter (PM2.5) on the associations between greenness and GDM were also explored.

RESULTS

During the first two trimesters of pregnancy, an increase in NDVI-500 m or NDVI-1000 m interquartile range was consistently associated with lower GDM risks, with adjusted odds ratios (aORs) and 95% confidence interval (CI) ranging from 0.82 (0.76, 0.88) to 0.90 (0.85, 0.96). Stratified analyses revealed that the health benefits of residential greenness are more pronounced during the first two trimesters among unemployed women (aOR = 0.70; 95%CI: 0.60, 0.82), those with lower education levels (aOR = 0.72; 95%CI: 0.63, 0.82), and those without medical insurance (aOR = 0.76; 95%CI: 0.69, 0.84). Mediation analysis shows that PM2.5 reduction by greenness may explain 16.4% of the inverse association between the NDVI-500 m during early pregnancy and the risk of GDM.

CONCLUSIONS

Our research indicates that elevated residential greenness was associated with reduced GDM risks, partly attributed to decreased PM2.5 levels. Women with lower SES experience amplified benefits from greenness. These findings highlight the significance of bolstering urban green infrastructure, particularly in communities confronting socioeconomic challenges and areas with high levels of air pollution.