Association of urinary cadmium with high sensitive C-reactive protein among the elderly aged 65 years and older in nine longevity areas of China

Background  The mechanism of cadmium damaging cardiovascular system is still unclear, and inflammation is considered to be one of the possible mechanisms. However, the epidemiological evidence of the association between cadmium and high sensitive C-reactive protein (hs-CRP) is limited.

Objective  This study aims to investigate the association of urinary cadmium level with hs-CRP among the elderly aged 65 years and older.

Methods  A total of 1860 participants aged 65 years and older were recruited in nine longevity areas from the Heathy Aging and Biomarkers Cohort Study between 2017 and 2018. Information including demographic characteristics, life styles, and diet was collected by questionnaire and physical examination. Meanwhile, venous blood and urine samples were collected to detect the levels of hs-CRP and urinary cadmium. Elevated hs-CRP was defined as hs-CRP >3.0 mg·L^-1. The respondents were stratified into three groups (low, middle, and high) according to the tertiles of creatinine-adjusted urinary cadmium level. Generalized linear mixed models were used to analyze the association of urinary cadmium with hs-CRP. In order to assess effect modifications by age and sex, stratified models with interaction terms were also constructed.

Results The age of the participants was (83.41±11.24) years, 917 (49.30%) participants were male, 529 (28.44%) participants aged >90 years, and 319 (17.15%) participants were defined as elevated hs-CRP. The median (P₂₅, P₇₅) urinary cadmium level after creatinine correction of the total participants was 1.12 (0.63, 2.06) μg·g^-1, and the levels of the participants with low, middle, and high urinary cadmium were < 0.79, 0.79-1.66 μg·g^-1, and ≥ 1.66 μg·g^-1, respectively. The rates of elevated hs-CRP were 15.44%, 17.77%, and 18.35% among the participants with low, middle, and high urinary cadmium, respectively (P > 0.05). After adjustment for sex, age, education, and other variables, for each increase of a natural logarithmic unit of urinary cadmium, the OR for elevated hs-CRP was 1.14 (95%CI: 0.96-1.36; P>0.05). Compared with the participants with low urinary cadmium, the OR s of elevated hs-CRP for the participants with middle and high urinary cadmium were 1.49 (95% CI: 1.04-2.13) and 1.58 (95% CI: 1.07-2.33), respectively (P < 0.05). The subgroup analysis results showed that compared with the participants with low urinary cadmium, the OR s of elevated hs-CRP in males and females with high cadmium were 1.82 (95% CI: 1.04-3.19) and 1.48 (95% CI: 0.91-2.41), and the OR s of elevated hs-CRP in ≤ 90 and >90 years participants with high cadmium were 1.85 (95% CI: 1.14-2.98) and 1.48 (95% CI: 0.78-2.80), respectively. Neither sex nor age modified the association between urinary cadmium and elevated hs-CRP (P_interaction > 0.05).

Conclusion A high urinary cadmium level is associated with elevated hs-CRP among the elderly aged 65 years and older in selected nine longevity areas in China.