Incident anaemia as a marker of cancer and all-cause mortality: evidence from 380 114 adults in the population-based Stockholm Early Detection of Cancer Study (STEADY-CAN) cohort

Objective: Anaemia is common in healthcare and may indicate undiagnosed cancer. Despite this, evidence regarding risk estimates informing clinical decision-making remains limited, particularly regarding haemoglobin dynamics and the role of mean corpuscular volume (MCV). We aimed to quantify the 18-month risks of incident cancer (IC) and all-cause mortality (ACM) following incident anaemia (IA), and to examine how MCV modifies these risks. Methods and analysis: Population-based, age- and sex-matched cohort study. The study used the Stockholm Early Detection of Cancer Study (STEADY-CAN), covering almost all adults residing in Stockholm County, Sweden, during 2011-2021. STEADY-CAN links laboratory tests with national registers, capturing healthcare use, diagnoses, cancer outcomes and prescribed medications.We included 190 057 adults with IA and 190 057 age- and sex-matched non-anaemic controls from the STEADY-CAN cohort. Eligible individuals were ≥18 years old, cancer-free, had ≥2 Hb measurements during 2011-2020 and a concurrent MCV value at the IA date. IA was defined as the first Hb value from 2012 onwards below 130 g/L in men or 120 g/L in women after prior normal values.Sex-stratified adjusted piecewise competing-risks multi-state Cox regression models were used, with separate HRs for IA during 0-3, 3-6, 6-12 and 12-18 months of follow-up. The main outcome measures were IC and ACM during the 18-month follow-up. Results: IC occurred in 6.2% of male and 2.8% of female IA cases, compared with 2.4% and 1.1% of controls. Corresponding ACM rates were 7.4% and 4.0% in IA cases versus 2.5% and 1.7% in controls. IA implied a 9.17-fold higher IC risk and 8.50-fold higher ACM risk among men during 0-3 months of follow-up, with 8.25- and 6.14-fold higher risks among women (all p