Smoking-Related Distortion of Haemoglobin Concentration May Alter Anaemia Classification and Population Burden Estimates.

Abstract

Introduction: Cigarette smoking can alter interpretation of measured haemoglobin near anaemia thresholds. We quantified the consequences of applying the World Health Organization (WHO) smoking adjustment.

Methods: We analysed National Health and Nutrition Examination Survey data from non-pregnant US adults aged ≥ 20 years reporting current cigarette smoking. The primary period was 2005-2016 (n = 6380), with 2017-March 2020 as an independently weighted replication period. We applied WHO cigarette-quantity adjustments to measured haemoglobin and estimated survey-weighted changes in anaemia classification, implementation sensitivity, and supportive haematologic phenotypes.

Results: Anaemia prevalence increased from 3.9% (95% CI, 3.4%-4.6%) before adjustment to 6.4% (5.7%-7.3%) after adjustment. The adjustment newly identified 217 participants, an absolute increase of 2.5 percentage points (2.1-3.0), representing approximately 1.08 million US adults and 38.7% of anaemia after adjustment. Sensitivity estimates for the absolute increase ranged from 2.3 to 2.5 percentage points. The independent-period increase was larger at 4.5 percentage points (3.2-6.2). Participants newly identified as anaemic had lower mean corpuscular volume, serum iron, and ferritin and higher red cell distribution width and soluble transferrin receptor; principal patterns were directionally concordant in the replication period.

Conclusions: Applying WHO smoking adjustment materially changed estimated anaemia prevalence and identified a threshold-adjacent group with a supportive haematologic and iron-status phenotype. Newly identified results warrant clinical confirmation and aetiologic evaluation rather than automatic treatment.