Type 1 diabetes diagnosed before age 10 carries the largest excess mortality

Design

Retrospective nationwide register cohort with matched population controls

Population

34,155 adults with type 1 diabetes and 150,026 controls, Sweden, 1998 to 2020

Primary outcome

All-cause, cardiovascular and non-cardiovascular mortality by age at diagnosis

Effect

All-cause mortality HR 0.98 (95% CI 0.98 to 0.99) per year later onset; onset 0 to 10 years vs controls HR 3.23 (2.92 to 3.58)

A Swedish nationwide cohort followed 34,155 adults with type 1 diabetes from the National Diabetes Register, registered between 1998 and 2019, against 150,026 matched people from the general population, through 2020.

Each one-year increase in age at diagnosis was associated with lower all-cause mortality (HR 0.98, 95% CI 0.98 to 0.99) and lower cardiovascular mortality (HR 0.97, 0.97 to 0.98). Put another way, diagnosis five years later was associated with about 8% lower mortality. The gap against matched controls was widest for those diagnosed between birth and age 10: all-cause mortality HR 3.23 (2.92 to 3.58) and cardiovascular mortality HR 5.73 (4.32 to 7.59).

This is about prognosis, not about a new treatment. Age at onset largely stands in for years of exposure to hyperglycaemia, so these adults reach midlife with decades of disease behind them. That makes them a group in whom cardiovascular and kidney risk deserve earlier and more deliberate attention than their age alone would suggest.

In clinic, record age at diagnosis as a risk factor, not a historical note, and use it when deciding how early to start statins, check albuminuria and screen for retinopathy in a young adult.

• Record age at type 1 diabetes diagnosis in every adult's risk assessment, not only current age.
• In a young adult diagnosed in early childhood, consider cardiovascular risk management earlier than age alone would prompt.
• Check urine albumin-to-creatinine ratio and eGFR annually from transition to adult care onwards.
• Treat lipids and blood pressure on cumulative diabetes duration, not on how young the patient looks.

Why it matters

Cardiovascular risk calculators built on age underrate the young adult who has had diabetes since early childhood.

Don't overread it

This is a register association; it cannot say that delaying onset, or any specific treatment, would change these risks.

The statistics, in plain English

A hazard ratio of 0.98 per year sounds tiny, but it compounds: across ten years of difference in onset age it adds up to a meaningful gap. The comparison with the general population (HR 5.73 for cardiovascular death in those diagnosed before 10) means their cardiovascular death rate was nearly six times that of matched peers. The intervals are narrow because the cohort is large, so the estimates are precise, but precision is not the same as causation.

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