Elucidating bidirectional relationship between metabolic syndrome and elevated faecal haemoglobin concentration: a Taiwanese community-based cohort study

OBJECTIVES: To elucidate the bidirectional temporal relationship between elevated faecal haemoglobin (f-Hb) concentration and metabolic syndrome (MetS). DESIGN: A longitudinal cohort study was conducted by utilising data on community-based periodical screening for colorectal cancer with faecal immunochemical test (FIT) and health check-up for MetS. SETTING: Population-based organised integrated service screening in Keelung city, Taiwan. PARTICIPANTS: We enrolled a total of 62,293 community residents aged 40–79 years. MAIN OUTCOMES AND MEASURES: Bidirectional outcomes of FIT-positive and MetS were measured. RESULTS: The presence of MetS at baseline led to a statistically significant 31% elevated risk of being incident FIT-positive (adjusted HR, (aHR)=1.31, 95% CI: 1.14 to 1.51) whereas the effect of those with FIT-positive at baseline on incident MetS was not statistically significant (aHR=1.06, 95% CI: 0.89 to 1.25) after adjusting for relevant confounders. Such an effect was particularly noted for three individual components (abnormal waist circumference, higher fasting plasma glucose and lower high-density lipoprotein). CONCLUSIONS: Our finding on the presence of MetS before FIT-positive based on bidirectional relationship assessment suggests the control of MetS may contribute to reducing the risk of colorectal neoplasia through the early surveillance of f-Hb. However, such a temporal epidemiological finding still needs to be verified by using other external data.