Findings from a new study have identified a link between passive smoking in childhood and the risk of rheumatoid arthritis (RA), and an association between a history of chronic diarrhoea and the risk of developing RA, both for the first time.
After analysing data from 70,598 female volunteers born between 1925 and 1950, scientists found passive smoking exposure during childhood increased the association between RA risk and adult active smoking. In smokers who had childhood passive exposure to smoke, the hazard ratio was 1.73 compared with non-smokers not exposed during childhood. In contrast, the hazard ratio was 1.37 in active smokers not exposed to passive smoke during childhood.
In a separate analysis, previous chronic diarrhoea was associated with more than double the risk of RA (hazard ratio of 2.32), while chronic constipation or alternating between diarrhoea and constipation did not impact risk (hazard ratios of 1.16 and 1.07 respectively).
The authors said their findings “perfectly fit with the preclinical scheme of RA, where an external event occurs at an early stage to promote emergence of auto-immunity, followed years after by clinical RA”.
The findings were presented at the Annual European Congress of Rheumatology (EULAR) 2017 this month.