Background: In recent years, few studies have quantified the effect of residential context on blood pressure. Although these studies have emphasized the importance of socioeconomic influences such as education or poverty levels, the association between the features of social structure such as social capital and blood pressure remain unclear. Therefore, we investigated whether social capital was associated with systolic blood pressure after controlling for individual potential confounders.
Methods: We analyzed data from the Shimane Study conducted from 2006 to 2008 in rural mountainous regions of Japan. After excluding the missing data and data of participants taking hypertension medication, we conducted a multilevel analysis of the data for 335 individuals nested within 30 postcode sectors.
Results: Systolic blood pressure increased with increasing age and body mass index. We also found that a higher systolic blood pressure was observed among smokers and those taking medication for diabetes. Regarding the contextual effects of social capital, systolic blood pressure increased with an increasing proportion of lack of fairness, after adjustment for individual confounders.
Conclusions: To the best of our knowledge, this study is the first to investigate the association between social capital and systolic blood pressure by using a multilevel methodological framework. Surprisingly, we found that lack of fairness had a strong effect on systolic blood pressure. However, we could not find any significant associations between other items of social capital and systolic blood pressure. Further studies are needed to clarify the mechanism by which lack of fairness may have an effect on systolic blood pressure.