Incidental lymphopenia and mortality: a prospective cohort study.
Level 3 - non-randomized controlled study
Prospective observational cohort study
PubMed 31932337 · doi:10.1503/cmaj.191024
What was done
In a prospective cohort study of 108,135 participants from the Copenhagen General Population Study (median age 68 years) followed between November 2003 and April 2015 for a median of 9 years (IQR 0–14), risks of all-cause and cause-specific mortality were evaluated using Cox proportional hazards regression across three lymphocyte count categories: below the 2.5th percentile (< 1.1 × 10⁹/L, lymphopenia), between the 2.5th and 97.5th percentiles (1.1–3.7 × 10⁹/L, reference), and above the 97.5th percentile.
What was found
During follow-up, 10,372 participants died. Compared to the reference group, lymphopenia (< 1.1 × 10⁹/L) was associated with multivariable-adjusted hazard ratios (HRs) of 1.63 (95% CI 1.51–1.76) for all-cause mortality, 1.67 (95% CI 1.42–1.97) for nonhematologic cancers, 2.79 (95% CI 1.82–4.28) for hematologic cancers, 1.88 (95% CI 1.61–2.20) for cardiovascular diseases, 1.88 (95% CI 1.55–2.29) for respiratory diseases, 1.86 (95% CI 1.53–2.25) for infectious diseases, and 1.50 (95% CI 1.19–1.88) for other causes. The highest absolute 2-year mortality risk was observed in smokers aged 80 or older with lymphocyte counts < 0.5 × 10⁹/L (61% in women, 75% in men). Lymphocyte counts above the reference category were also associated with higher mortality (adjusted HR 1.17, 95% CI 1.04–1.31).
Why it matters
Incidental lymphopenia detected on routine complete blood counts is strongly associated with elevated broad-spectrum mortality, indicating it could serve as an accessible clinical marker for vulnerability and subclinical disease.
Limits
The observational design cannot establish causality or rule out residual confounding from unmeasured acute or chronic conditions. The study was conducted in a single population cohort from Copenhagen, limiting generalizability to other geographic or ethnic populations. Specific lymphocyte subpopulations and longitudinal changes in counts were not reported in the abstract.
Cited by
- supports Cancer hazard risk begins to increase around an absolute lymphocyte count below 1,000 cells/µL, while a normal youthful range is 1,500 to 3,000 cells/µL.