The association between systemic immune-inflammation index and prostate-specific antigen: Results from NHANES 2003-2010.

Purpose: Current research has not extensively explored the correlation between Systemic Inflammatory Index (SII) and prostate-specific antibody (PSA) levels. This study aimed to investigate the relationship between the SII and PSA levels in American males aged > 40 years without prostate cancer.

Methods: Data were obtained from the 2003-2010 National Health and Nutrition Examination Survey (NHANES). Patients without complete SII or PSA data were excluded. Multiple linear regression models were used to investigate the possibility of a linear association between the SII and PSA levels. Fitted smoothed curves and threshold effect analyses were used to characterize the nonlinear relationships.

Results: The study included 5982 male participants over the age of 40 years from the United States. The average SII (mean ± standard deviation) was 562.78 ± 355.60. The mean value of PSA was 1.85 ± 3.24. The results showed that SII exhibited a positive correlation with PSA (β = 0.0005, 95% CI: (0.0002, 0.0007)), and an interaction test indicated that the effects of age, body mass index, hypertension, and diabetes were not significant for this positive correlation between SII and PSA (all P > 0.05). We discovered an inverted U-shaped connection between the SII and PSA with a turning point (K) of 1168.18 by using a two-segment linear regression model. To the left of the turning point, there was a positive connection between SII and PSA (β = 0.0009,95% CI: (0.0006, 0.0012); P < 0.0001).

Conclusion: In the population of men over 40 years old without prostate cancer, SII and PSA exhibited a non-linear relationship. Specifically, there was a positive correlation between SII and PSA levels when the SII value was < 1168.18.