Proportional hazards models in epidemiology

This article examines the factors influencing age at death in the multiethnic villages, comprised mostly of Georgians and Ossets, in the Kistauri commune in the eastern Republic of Georgia between 1897 and 1997. The data are analyzed with Cox proportional hazards models using age at death as the dependent variable, and ethnicity, gender, marital status, residency status, and year of birth as the independent variables. The results show that Georgians lived longer than Ossets. Individuals who had ever been married lived longer than those who had not. The results perhaps reflect harsher living conditions for Ossets, the ethnic minority, despite Soviet ideologies about equality.

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The prognostic role of plasma fibrinogen in adult secondary hemophagocytic lymphohistiocytosis

Orphanet Journal of Rare Diseases ◽

10.1186/s13023-020-01622-2 ◽

2020 ◽

Vol 15 (1) ◽

Author(s):

Guangli Yin ◽

Changfeng Man ◽

Jiayu Huang ◽

Shengen Liao ◽

Xin Gao ◽

...

Keyword(s):

Hemophagocytic Lymphohistiocytosis ◽

Inflection Point ◽

Proportional Hazards ◽

Cubic Spline ◽

Cox Proportional Hazards ◽

Plasma Fibrinogen ◽

Proportional Hazards Models ◽

Cox Proportional Hazards Models ◽

Cubic Spline Curve ◽

Secondary Hemophagocytic Lymphohistiocytosis

Abstract Background In adult patients with secondary hemophagocytic lymphohistiocytosis (sHLH), no valid immune biomarker has been available for predicting the prognosis of untreated sHLH patients. Methods Circulating plasma levels of fibrinogen (FIB) were measured at diagnosis in 293 cases of adult sHLH. We categorized FIB levels into tertiles. Multivariable Cox proportional hazards models were used to evaluate the relationship between FIB and survival. Restricted cubic spline models and two-piecewise Cox proportional hazards models were used to address the nonlinear association between FIB and mortality. Results During a median follow-up of 52 (interquartile ranges, 18–221) days, 208 deaths occurred, with 137 deaths in malignancy-associated hemophagocytic lymphohistiocytosis (MHLH) and 71 deaths in non-malignancy-associated hemophagocytic lymphohistiocytosis (non-MHLH). After multivariable adjustment, compared with the highest tertile of FIB, the hazard ratios (HRs) with 95% confidence intervals (CIs) of survival for tertile 2 and tertile 1 were 1.06 (0.90–1.24) and 0.84 (0.71–0.98), respectively. The restricted cubic spline curve displayed a nonlinear and inverse relationship between FIB and mortality. Furthermore, the threshold effect analysis demonstrated that the inflection point for the curve was at an FIB level of 1.76 g/L. The HRs (95% CIs) for survival were 0.68 (0.55–0.83) and 1.08 (0.96–1.21) on the left and right side of the inflection point, respectively. Conclusions These results suggest that plasma fibrinogen is nonlinearly and inversely associated with the risk of mortality in adult secondary hemophagocytic lymphohistiocytosis.

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