Incidental lymphopenia and mortality: a prospective cohort study

Area of Science:

• Clinical Medicine
• Epidemiology
• Hematology

Background:

• The prognostic significance of incidental lymphopenia in the general population remains unclear.
• Investigating the association between lymphopenia and mortality is crucial for public health.

Purpose of the Study:

• To determine the relationship between lymphopenia and all-cause mortality.
• To identify associations between lymphopenia and cause-specific mortality.

Main Methods:

• Prospective cohort study of 108,135 participants from the Copenhagen General Population Study (2003-2015).
• Analysis using Cox proportional hazards regression to model mortality risks based on lymphocyte count percentiles.
• Participants categorized into three groups: below 2.5th percentile (lymphopenia), 2.5th-97.5th percentile (reference), and above 97.5th percentile.

Main Results:

• Lymphopenia (< 1.1 × 10^9/L) was associated with significantly higher all-cause mortality (HR 1.63) and cause-specific mortality, including non-hematologic cancers (HR 1.67), hematologic cancers (HR 2.79), cardiovascular diseases (HR 1.88), respiratory diseases (HR 1.88), and infectious diseases (HR 1.86).
• Increased mortality risk was also observed for lymphocyte counts above the reference range (HR 1.17).
• The highest absolute 2-year mortality risks were seen in elderly smokers with very low lymphocyte counts (< 0.5 × 10^9/L).

Conclusions:

• Lymphopenia is a significant independent risk factor for increased all-cause and cause-specific mortality in the general population.
• These findings underscore the clinical relevance of lymphocyte counts in predicting mortality risk.
• Further research may explore the underlying mechanisms linking lymphopenia to adverse health outcomes.