Associations of triglyceride glucose-body mass index and the combination of sedentary behavior and physical activity with risks of all-cause mortality and myocardial infarction: a cohort study from the UK biobank

BACKGROUND: Triglyceride glucose-body mass (TyG-BMI) index, sedentary behavior (SB) and physical activity (PA) are independently associated with all-cause mortality and myocardial infarction (MI). However, it remains unclear whether TyG-BMI index and the combination of SB and PA exhibit joint effects on all-cause mortality and MI. METHODS: Among 502 356 participants from the UK Biobank, 297 761 eligible participants were selected. The Cox proportional hazards model and the restricted cubic spline regression model were used to assess the associations of TyG-BMI with all-cause mortality and MI. To conduct stratified analysis, participants were classified into four groups by SB (<6 h/d and ≥ 6 h/d) and moderate to vigorous physical activity (MVPA) (<150 min/wk and ≥ 150 min/wk). Additionally, the multiplicative interaction was assessed between TyG-BMI and SB & MVPA. Furthermore, to estimate their joint associations, participants were conjointly classified into twelve new groups by TyG-BMI (tertiles) and SB & MVPA (four groups). RESULTS: During a median follow-up of 13.8 and 13.6 years, 21 335 deaths and 9 116 MI were observed, respectively. The dose-response relationship of TyG-BMI with all-cause mortality was U-shaped with a cut-off point at 225.09, whereas the relationship with MI was positive nonlinear with a cut-off point at 266.87. A synergistic effect on all-cause mortality was observed between TyG-BMI tertile 1 and ≥ 6 h/d SB & <150 min/wk MVPA (P for interaction < 0.001). When MVPA ≥ 150 min/wk combined with SB either <6 h/d or not, TyG-BMI tertile 2 showed no significant association with all-cause mortality risk, with HRs(95%CIs) of 0.98 (0.93-1.03) for <6 h/d SB and 1.00 (0.94-1.07) for ≥ 6 h/d SB. When one of the two healthy behaviors was present (i.e., either <6 h/d SB with <150 min/wk MVPA, or ≥ 150 min/wk MVPA with ≥ 6 h/d SB), its combination with TyG-BMI tertile 1 showed no significant association with MI risk, with HRs(95%CIs) of 1.07(0.95-1.20) and 1.09(0.94-1.25), respectively. CONCLUSIONS: TyG-BMI index and the combination of SB and PA were independently and jointly associated with risks of all-cause mortality and MI. Our findings highlight the importance of improving insulin resistance to reduce all-cause mortality risk, particularly in individuals with long-term SB and insufficient PA, who are more susceptible to the adverse effects of TyG-BMI index. In long-term sedentary individuals, meeting PA guidelines (≥ 150 min/wk of MVPA) effectively mitigated risks of all-cause mortality and MI associated with TyG-BMI index.