Population-based register study of children born in Sweden from 1997 to 2014 showed an increase in rickets during infancy.

AIM

This population-based study assessed the incidence of rickets in infants up to age of one born in Sweden from 1997 to 2014. We also examined maternal and perinatal factors and co-morbidity.

METHODS

We used Swedish National Board of Health and Welfare registers and data from Statistics Sweden. The outcome measure was an International Classification of Diseases, Tenth Revision, code for rickets.

RESULTS

There were 273 cases of rickets, with an incidence of 14.7 per 100 000 and a 10-fold incidence increase between 1997 and 2014. The majority (78.4%) were born preterm, half were small-for-gestational age (SGA) (birthweight <10th percentile), 4.8% were born to Asian-born mothers and 3.5% to African-born mothers. The adjusted odds ratios by birth week were 182 (95% CI: 121-272) before 32 weeks and 10.8 (95% CI: 6.72-17.4) by 32-36 weeks. Preterm infants with necrotising enterocolitis had very high odds for rickets and so did SGA term-born infants and those born to African-born mothers. The odds for rickets among preterm infants increased considerably during the later years.

CONCLUSION

Rickets increased 10-fold in Sweden from 1997 to 2014 and was mainly associated with prematurity, SGA and foreign-born mothers. Possible reasons may include increased preterm survival rates and improved clinical detection and registration.