Hazard ratios [ 95 % confidence intervals ( CI ) ] for HF were 1.0 ( ref ) , 0.86 ( 0.72-1 .03 ) , 0.80 ( 0.66-0 .98 ) , 0.92 ( 0.74-1 .13 ) , and 0.82 ( 0.63-1 .07 ) , for chocolate consumption of less than 1/month , 1-3 / week , 2-4 / week , and 5 + / week , respectively , after adjusting for age , body mass index ( BMI ) , smoking , alcohol , exercise , energy intake , and history of atrial fibrillation ( P for quadratic trend = 0.62 ) .