Association of fish intake with all-cause mortality according to CRP levels or inflammation in older adults: a prospective cohort study

Background: The relationship between inflammatory response, fish consumption, and mortality risk in older individuals is unclear. We investigated whether C-reactive protein (CRP) levels ≥ 0.1 mg/dL, fish intake, and inflammatory responses are associated with all-cause mortality risk in older adults.

Methods: This prospective cohort study included older adults aged 85-89 years from the Kawasaki Aging and Wellbeing Project, who did not require daily care. Cohort was recruited from March 2017 to December 2018 (follow-up ended on December 31, 2021). Dietary assessment was conducted using the Brief Self-Administered Diet History Questionnaire. Multivariate Cox proportional hazards regression was used to estimate the hazard ratio (HR) and 95% confidence interval (CI) for all-cause mortality in the CRP ≥ 0.1 mg/dL group; the CRP < 0.1 mg/dL group was used for reference. Within CRP ≥ 0.1 and < 0.1 mg/dL groups, participants were categorized into tertiles of fish intake. HRs and 95% CIs for all-cause mortality in the other groups were estimated using the lower tertile group as a reference.

Results: The study included 996 participants (mean [standard deviation] age, 86.5 [1.37] years; 497 [49.9%] women) with a median CRP level of 0.08 (interquartile range [IQR] = 0.04-0.16). There were 162 deaths during 4,161 person-years of observation; the multivariable-adjusted HR for all-cause mortality in the CRP ≥ 0.1 mg/dL group was 1.86 (95% CI, 1.32-2.62); P < 0.001. In 577 individuals with median (IQR) fish intake of 39.3 g/1000 kcal (23.6-57.6) and CRP level of < 0.1 mg/dL, the multivariable-adjusted HR for all-cause mortality in the higher tertile group of fish intake was 1.15 (0.67-1.97); P = 0.59, non-linear P = 0.84. In 419 individuals with median (IQR) fish intake of 40.7 g/1000 kcal (25.0-60.1) and CRP level of ≥ 0.1 mg/dL, the multivariate-adjusted HR for all-cause mortality in the higher tertile group of fish intake was 0.49 (0.26-0.92); P = 0.026, non-linear P = 0.38, P-value for interaction = 0.040.

Conclusions: A negative association between fish intake and all-cause mortality was seen in older adults with elevated CRP levels, which is a mortality risk factor. While the results may be limited owing to stringent methods ensuring impartiality, they offer valuable insights for future research.

Trial registration: UMIN000026053. Registered February 24, 2017.