Objective: To investigate genetic and lifestyle factors and their interactions on plasma homocysteine (Hcy) concentrations in the Boston Puerto Rican population.
Design: Cross-sectional study. Plasma concentrations of Hcy, folate, vitamin B12 and pyridoxal phosphate were measured, and genetic polymorphisms were determined. Data on lifestyle factors were collected in interviews.
Setting: A population survey of health and nutritional measures.
Subjects: A total of 994 Puerto Rican men and women residing in the Boston metropolitan area.
Results: Smoking status was positively associated with plasma Hcy. Genetic polymorphisms MTHFR 677C→T, FOLH1 1561C→T, FOLH1 rs647370 and PCFT 928A→G interacted significantly with smoking for Hcy. MTHFR 1298A→C (P = 0·040) and PCFT 928A→G (P = 0·002) displayed significant interactions with alcohol intake in determining plasma Hcy. Subjects with PCFT 928GG genotype had significantly higher plasma Hcy concentrations compared with carriers of the A allele (AA+AG; P = 0·030) among non-drinking subjects. When consuming alcohol, GG subjects had lower plasma Hcy levels compared with AA+AG subjects. Physical activity interacted significantly with MTR 2756A→G in determining plasma Hcy (P for interaction = 0·002). Smoking interacted with physical activity for plasma Hcy (P for interaction = 0·023).
Conclusions: Smoking and drinking were associated plasma Hcy concentrations. Genetic variants involved in folate metabolism further modify the effects of lifestyle on plasma Hcy.