Birthweight, body size, and growth during childhood and risks of rheumatoid arthritis: a large Danish cohort study

Abstract

Objectives

Adult obesity may be positively associated with risks of rheumatoid arthritis (RA), but associations with early life body size are unknown. We examined whether birthweight, childhood body mass index (BMI), height, and changes in BMI and height were associated with risks of adult RA.

Method

A cohort of 346 602 children (171 127 girls) from the Copenhagen School Health Records Register, born in 1930–1996, with measured weights and heights from 7 to 13 years of age, were included. Information on RA, including serological status, came from national registers from 1977 to 2017. Cox regressions were performed.

Results

During a median of 35.1 years of observation time per person, 4991 individuals (3565 women) were registered with RA. Among girls, per BMI z-score, risks of RA and seropositive RA increased by 4–9% and 6–10%, respectively. Girls with overweight had higher risks of RA than girls without overweight. Girls who became overweight by 13 years of age had increased risks of RA compared to girls without overweight at 7 or 13 years (hazard ratio = 1.40, 95% confidence interval 1.19–1.66). For boys, associations between BMI and RA (including seropositive RA) were not statistically significant. Height was not associated with RA (any type) in girls. Taller boys had higher risks of RA, especially seropositive RA. Birthweight was not associated with RA.

Conclusions

Among women, childhood adiposity was associated with increased risks of RA. Among men, childhood height was positively associated with risks of RA. These findings support the hypothesis that early life factors may be important in the aetiology of RA.

Acknowledgements

The Copenhagen School Health Records Register was initiated and planned by Dr Thorkild IA Sørensen and built by the Institute of Preventive Medicine, The Capital Region of Denmark.

Funding

Funding for this study was received from Novo Nordisk Foundation [NNF18OC0052871 and NNF17OC0028338] and The Danish Rheumatism Association [A3865] .

Data availability statement

The data used in this study are based on a combination of data with personal identification numbers from third parties, the Copenhagen School Health Records Register, hosted by the Center for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospital, and data from national health registers. According to Danish law, this information cannot be made publicly available. Access to the subset of data included in this study can be gained through submitting a project application to the corresponding author, Jennifer L Baker, and pending approval by the data steering committee.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.