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

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

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.

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.

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.