Rising Cancer Deaths in New Zealand’s Youngest: A Decade Review

Overview

An analysis of cause-of-death data from 2013 to 2022, using the Ministry of Health’s ICD-10 coded mortality dataset (Chapter 2: Neoplasms), reveals a stable but very small number of cancer deaths among New Zealand children aged 0–4. Special emphasis is placed on infants under one year of age (age group “0”), where a coding anomaly appears in 2022.

Key Findings

Cancer Mortality Counts

Corrected Observations

• Absolute numbers of cancer deaths are very small (single digits per year), unlike the much larger figures in the earlier draft.

• The proportion of infant deaths within the 0–4 group fluctuates year to year but generally sits between 25–45%.

• In 2022, infants represented 37.5% of all 0–4 cancer deaths (3 of 8). While elevated relative to 2021 (14.3%), it is not a record high across the decade (45.5% was recorded in 2013).

Subgroup Trends

A closer look at cancer subgroups shows:

Infants (Age 0, 2013–2022):

• Digestive organ cancers (C15–C26) appeared for the first time in 2022 (1 case).

  

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• Thyroid/endocrine cancers (C73–C75) occurred in 2018 (1 case) and 2019 (2 cases), but were absent in 2020–2022.

• Brain/CNS cancers (C69–C72) were present intermittently in earlier years but not in 2022.

• The 2022 total of 3 infant cancer deaths consisted of:

  • 1 digestive organ cancer,

  • 1 benign neoplasm,

  • 1 neoplasm of uncertain/unknown behavior.

Children (Ages 1–4, 2022):

• 5 cancer deaths recorded.

• These included 3 brain/CNS cancers, 1 urinary tract cancer, and 1 thyroid cancer.

• Notably, thyroid cancers remained present in 2022 for ages 1–4, while disappearing only for infants.

Interpretation of Subgroup Anomaly

The dataset confirms a substitution-like anomaly in infants:

• Digestive cancers appear for the first time in 2022.

• Thyroid cancers vanish, while remaining present in ages 1–4.

This suggests a pattern that is specific to infants rather than a coding change applied across the full 0–4 age band.

Expanded Context

• Infant cancer mortality is extremely rare in New Zealand, typically 2–5 cases per year.

• The dataset does not support claims of dozens of infant cancer deaths per year.

• Broader ICD analysis (beyond cancer) shows larger increases post-2020 in categories such as perinatal conditions (Chapter 16) and ill-defined conditions (Chapter 18), which may warrant separate review.

Next Steps

• Analyze whether this pattern persists into 2023 once data becomes available.
• Conduct normalization by birth cohort size to determine if the mortality rate per 1,000 births also increased.
• Examine ICD subgroup breakdowns for cancer types contributing to the infant death spike.
• Further investigate causes behind the rise in deaths recorded under Chapter 18 and Chapter 22.
• Consider whether internal MoH or DHB coding guidance may have shifted classification practices mid-decade.

Data Source: Ministry of Health NZ, ICD-10 Chapter 2 and full-cause mortality data (2013–2022).

Were More Babies Born?

To test whether these increases might simply reflect a growing infant population, we examined annual average birth cohort sizes (proxied by age 0 population):

The 2021 birth cohort was modestly larger than surrounding years, but not enough to explain the sharp post-2020 increases in infant deaths. 2020 and 2022 were typical and align with pre-pandemic norms.