Lifestyle factors, metabolic syndrome and apolipoprotein E in monozygotic twins with, at risk of and without affective disorders, as predictors of onset or recurrence of affective episodes, a seven-years follow-up study

INTRODUCTION: This study explores lifestyle factors, metabolic syndrome (MetS), apolipoprotein E genotype (APOE), and plasma concentrations of apoE as predictors for the onset and recurrence of affective disorders. METHODS: We examined these factors in a seven-year follow-up study of 201 monozygotic twins (MZ) with unipolar or bipolar disorder (affected), their unaffected co-twins (high-risk), and twins with no personal or familial risk of affective disorder (low-risk). RESULTS: Higher body mass index (hazard ratio (HR) = 1.29, 95 % CI 1.11-1.50) and higher apoE plasma concentrations (HR = 1.09, 95 % CI 1.02-1.17) were significant predictors of onset. The APOE genotypes ε22 (HR = 2.85, 95 % CI 1.52-5.36) and ε43 + ε44 (HR = 2.42, 95 % CI 1.42-4.11) were predictors of onset or recurrence in the total sample. The ε22 genotype increased the HR = 5.04(95 % CI 2.25-11.31) in the affected group, while ε43 + ε44 genotypes predicted onset in the high-risk group (HR = 7.42, 95 % CI 1.76-31.36). Smoking was a predictor of onset or recurrence of affective episodes in the overall sample (HR = 2.15, 95 % CI 1.24-3.74) and in the low-risk group (HR = 39.10, 95 % CI 2.75-555.33). CONCLUSIONS: The established risk genotypes APOE ε43 and ε44 were linked to the onset and recurrence of affective disorders in both affected and high-risk twins. Body mass index and smoking also emerged as significant risk factors. Furthermore, the predictors investigated may demonstrate different trajectories depending on familial risk for affective disorders. Overall, these findings underscore the importance of incorporating both biomarkers of and lifestyle factors into the prevention and treatment of patients with affective disorders.