Results in brief

• 97% of the cohort children had been dispensed one or more courses of antibiotics by the time they were five years of age.
• 62% had been dispensed antibiotics in the first year of life with 82%, 92% and 95% in the first two, three and four years respectively.
• A higher proportion of Māori and Pacific children than European children were dispensed an antibiotic course during each year of life.
• Māori and Pacific children were dispensed their first course of antibiotics at younger ages than other European or Asian children. Median ages for first courses were: Pacific 6.9 months, Māori 8.1 months, all others 10.8 months.
• The proportion of children who had been dispensed a course of antibiotics in each month of life increased steadily during the first year, peaking in the twelfth month at one in five children, then declining with age.
• Marked seasonal variation was superimposed on the age-related pattern with twice as many courses dispensed during the winter quarter (June to August) compared to the summer quarter (December to February).
• Each child was dispensed a median of eight antibiotic courses by age five years.
• Children of Māori, Pacific, and Asian ethnicities all received a significantly higher median number of courses than children of European ethnicity.
• Antibiotics were dispensed to Māori, Pacific and Asian children more frequently than to European children, even when correcting for socio-economic deprivation.
• Children living in households of high economic deprivation were dispensed antibiotics more frequently than those in low socioeconomic deprivation areas.
• The dispensing rate was lower for children living in rural compared with urban areas.

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The study, published this week in the Journal of Antimicrobial Chemotherapy describes community antibiotic dispensing for more than 5,000 children in the contemporary longitudinal study of child development Growing Up in New Zealand, during their first five years. The Growing Up in New Zealand child cohort has been shown to be generalisable to the total New Zealand birth cohort in terms of ethnicity and socioeconomic diversity.

Dispensing data were obtained, with parental consent, through linkage with national pharmaceutical dispensing records. By five years of age, almost all (97%) children had received one or more antibiotic courses with a median of eight courses per child and an average rate of almost two courses per child per year.

Study author and infectious disease specialist Dr Mark Hobbs says that overall levels of antibiotic dispensing in New Zealand are higher than in the United States and many European countries with the highest levels being for young children and the elderly.

“In this study, we found that Māori and Pacific children received more antibiotic courses than New Zealand European children, as did children living in areas of high socioeconomic deprivation compared with those in the least deprived areas.

“Over one-third of the courses were dispensed during the three winter months and the majority of antibiotic courses were for one antibiotic drug, amoxicillin,” says Dr Hobbs. “This suggests to us that many of these courses are likely to have been for seasonal respiratory tract infections which are mostly caused by viruses. Antibiotic treatment is not effective in these circumstances and is not supported by New Zealand general practice guidelines.”

Antibiotic prescribing decisions for children in general practice often relate to doctors’ perceptions of parents’ expectations when seeking healthcare, as well as parents’ beliefs about antibiotics. A recent international survey by the World Health Organization revealed a poor level of public understanding about the situations where it is appropriate to use antibiotics.

The study authors expressed concern that prescribing such a lot of antibiotics for young children unnecessarily could have serious long term consequences, most importantly encouraging the spread of antibiotic-resistant bacteria.

Recent research has also shown that the first three years of life is a critical period for establishing a healthy microbiome – the healthy communities of bacteria that live in our gut, on our skin and elsewhere. It has been suggested that consumption of antibiotics at a young age may interfere with the developing microbiome and lead to permanent changes in immunity or metabolism.

“There is increasing evidence linking antibiotic use in young children to later weight gain and the development of chronic diseases, with asthma being one example,” says Dr Hobbs.

“Our finding that more than nine out of ten children had been exposed to antibiotics by three years of age is concerning for this reason. The large, ethnically and socioeconomically diverse Growing Up in New Zealand cohort gives us an ideal opportunity to investigate this possibility as the children develop.

“We also intend to review general practice medical records to get a better understanding of the reasons for antibiotic prescribing.

“Together, we expect these investigations will provide evidence to help manage the challenges of antibiotic use in primary care including addressing parents’ beliefs and expectations and supporting practitioners in balancing benefits versus harms in antibiotic prescribing.”

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Download the paper

Hobbs MR, Grant CC, Ritchie SR, Chelimo C, Morton SMB, Berry S, Thomas MG. (2017) Antibiotic consumption by New Zealand children: exposure near-universal by the age of five years. Journal of Antimicrobial Chemotherapy published online:doi: 10.1093/jac/dkx060

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