Regular Use of Fish Oil Supplements, Life's Essential 8 Score, and Cardiovascular Mortality in People With Type 2 Diabetes: A Longitudinal Cohort Study.

Background: To date, to our knowledge, no studies have investigated the effects of cardiovascular health on the cardioprotective benefits of fish oil supplementation in people with type 2 diabetes (T2D). The utility of fish oil in reducing risk of cardiovascular disease (CVD)-related mortality in people with diabetes remains unclear and inconsistent.

Objectives: This study aimed to investigate the potential modifying effect of cardiovascular health (CVH) level, as assessed using the Life's Essential 8 (LE8) score, on the association between regular fish oil supplement use and CVD-relates mortality in middle-aged and older people with T2D.

Methods: Participants with T2D in the UK Biobank were included. CVH level was categorized by the mean LE8 score (55 points). Multivariable-adjusted Cox models were used to evaluate the longitudinal association between regular use of fish oil supplements and CVD Mortality. We performed stratified analysis across different CVH levels and tested for potential interaction between fish oil supplement use and CVH level.

Results: The analysis included 19,003 participants (mean age: 59.9 ± 6.9 y, 36.1% women), of whom 39.6% were regular users of fish oil supplements. During a median follow-up of 13.7 y, regular use of fish oil supplements was significantly associated with lower risk of CVD Mortality among participants with better CVH [ie, LE8 score of ≥55 points; hazard ratio (HR): 0.65; 95% CI: 0.51, 0.84; P = 0.001)], but not among those with poorer CVH (i.e. LE8 score <55 points; HR: 1.02; 95% CI: 0.83, 1.25; P = 0.867). The interaction between the use of fish oil supplements and CVH level on CVD Mortality was significant (P = 0.018).

Conclusions: Middle-aged and older T2D individuals with a relatively low baseline CVH level may not obtain cardiovascular benefits from fish oil supplements. Our findings highlight the importance of promoting multimodal lifestyle interventions to improve survival outcomes of people with T2D.