Association of serum fatty acids with adverse long-term survival among cancer patients

Background: Evidence regarding the health effects of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and total polyunsaturated fatty acids (PUFAs) is controversial. Our objective was to explore the associations between serum-free fatty acids and mortality among cancer survivors. Methods: The study included 6,575 participants with or without cancer diagnosis aged 20 years and older with or without a cancer diagnosis who were recruited before December 2014 and followed up through December 31, 2019. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated by investigating weighted Cox proportional hazards regression models to assess the associations stratified by cancer status. Results: The weighted mean age was 49.6 years, 48.5% were male, and approximately 9.2% of the participants had a diagnosis of cancer. In total, there were 901 deaths over a median follow-up period of 8.74 years. After full adjustment for covariates, the positive associations between several subtypes of long-chain SFAs (C12:0-C16:0) and mortality risk were especially significant among cancer survivors (HRs per an increase of standard deviation 1.29–1.35, each p ≤ 0.022), while very-long chain SFAs (C22:0 and C23:0) were associated with reduced all-cause mortality only among adults without cancer (both p ≤ 0.029). There was substantial heterogeneity in the associations of individuals with different MUFAs with all-cause mortality stratified across cancer status. Omega-3 PUFAs were not related to mortality risk among adults with or without cancer (each p ≥ 0.086), while the individuals of omega-6 PUFAs (C18:2 n-6, C20:3 n-6, C22:4 n-6, and C22:5 n-6) were significantly associated with all-cause mortality risk among cancer survivors but not among those in the health population. Conclusions: We found that some subtypes of long-chain SFAs, MUFAs, and omega-6 PUFAs might be associated with increased all-cause mortality risk, while omega-3 PUFAs are not associated with reduced or increased mortality risk among cancer survivors.