Relationship between the advanced lung cancer inflammation index (ALI) and all-cause and cause-specific mortality among patients with chronic obstructive pulmonary disease (COPD): a population-based study

Chronic obstructive pulmonary disease (COPD) is viewed as a significant health problem, and the prognosis of patients with this disease is strongly influenced by the inflammatory response and nutritional well-being of the body. The advanced lung cancer inflammation index (ALI) provides a complete measurement of these two factors. Although the ALI has promising applications, its relationship with the prognosis of COPD patients remains unexplored. This research sought to bridge this knowledge gap by investigating the connection between the ALI and the outcomes of COPD patients. This study retrospectively investigated 2,884 COPD patients who were admitted to the respiratory department because of acute exacerbation. The study period extends from January 1, 2017, to December 31, 2022. All these COPD patients subsequently received follow-up, and the cause-specific and all-cause mortality of these patients was reported. Kaplan‒Meier analysis was employed to investigate the associations of the ALI with all-cause mortality and mortality resulting from specific causes among COPD patients. In addition, univariable and multivariable Cox proportional hazards models were used to explore this association in further detail after adjusting for various confounding variables. A restricted cubic spline (RCS) analysis was performed to assess the nonlinear relationships of the ALI with all-cause and cause-specific death rates among COPD patients. In addition, subgroup and sensitivity analyses were conducted to verify the validity of the findings. In total, 2,884 patients with COPD were recruited. A greater ALI was strongly associated with a lower risk of all-cause mortality and mortality resulting from respiratory and cardiovascular illnesses specifically among patients with COPD. The findings of the RCS analysis indicated a reverse J-shaped, nonlinear relationship between ALI and all-cause mortality among COPD patients, and an inflection point was identified at 95 (p for nonlinearity <0.0001). The inflection point of the J-shaped pattern indicates the ALI that is associated with the lowest risk of mortality. For ALIs less than 95, an increase of 10 units in the ALI was associated with a 14% reduction in the possibility of all-cause mortality (HR: 0.86; 95% CI: 0.81–0.92; p for trend=0.01). However, when the ALI was greater than 95, a 10-unit increase in the ALI resulted in a 5% increase in the likelihood of all-cause mortality (HR: 1.05; 95% CI: 1.01–1.07; Ptrend=0.01). Similar J-shaped patterns were observed for deaths related to cardiovascular and respiratory illnesses, in which context the inflection points were 97 and 96, respectively. These findings were consistent across various medical history and demographic subgroups and remained stable during the sensitivity analysis. This study revealed a unique relationship between a high ALI and a low risk of death among COPD patients. Additionally, the relationships between the ALI and mortality (both all-cause and from specific causes) exhibited nonlinear, J-shaped patterns. These findings indicate the potential for maintaining ALI within a specific range to improve long-term survival outcomes for patients with COPD.