Skin color, social classification, and blood pressure in southeastern Puerto Rico.

Objectives: We tested competing hypotheses for the skin color-blood pressure relationship by analyzing the association between blood pressure and 2 skin color variables: skin pigmentation and social classification.
Methods: We measured skin pigmentation by reflectance spectrophotometry and social classification by linking respondents to ethnographic data on the cultural model of "color" in southeastern Puerto Rico. We used multiple regression analysis to test the associations between these variables and blood pressure in a community-based sample of Puerto Rican adults aged 25-55 years (n=100). Regression models included age, gender, body mass index (BMI), self-reported use of antihypertensive medication, and socioeconomic status (SES).
Results: Social classification, but not skin pigmentation, is associated with systolic and diastolic blood pressure through a statistical interaction with SES, independent of age, gender, BMI, self-reported use of antihypertensive medication, and skin reflectance.
Conclusion: Our findings suggest that sociocultural processes mediate the relationship between skin color and blood pressure. They also help to clarify the meaning and measurement of skin color and "race" as social variables in health research.