If you are comparing idiopathic developmental intellectual disability across ages, the pattern is not a sudden adult drop — high-income-country prevalence stays broadly stable through the thirties before declining across later bands.

You are checking an age band for idiopathic developmental intellectual disability and need a plain answer: does the rate change sharply as people grow older?

For high-income countries, GBD 2023 records a fairly stable prevalence rate from ages 5-9 through ages 35-39.

The rate then declines across later age bands, reaching 398 per 100,000 at ages 60-64.

That pattern comes from the GBD Results tool, using both-sex estimates for 2023.

The sections below separate three measures: prevalence, the number of people living with the condition, and total disease burden measured in DALYs.

Before the sections open, the figures this page stands on — each one carrying its own source.

What GBD 2023 measures by age

You arrived looking for an age answer, so the first distinction matters: the dataset reports rates, counts, and DALYs as separate measures.

Prevalence tells you how many people per 100,000 were living with idiopathic developmental intellectual disability in each age band.

The count gives the estimated number of people in that band.

DALYs provide a separate disease-burden measure. They should be read beside the prevalence rate, rather than treated as another name for the number of people.

Every estimate here covers both sexes in high-income countries during 2023. The age bands run from under 1 year through ages 60-64.

Across the listed ages, the prevalence rate sits between 398 per 100,000 and 569 per 100,000. That range describes the dataset’s age pattern.

Seven reading points will help you follow the pattern: early childhood, school age, adolescence, early adulthood, the thirties, midlife, and later adulthood.

Seeing all the age bands together makes the answer easier to judge. Pick the line that matches the age you are examining.

The full comparison shows a gentle rise from under 1 year into ages 5-9, followed by a long period close to 0.6%. The later bands move downward.

Under 1 and ages 2-4 show the early childhood baseline

If the age in front of you falls in early childhood, the recorded rate sits below the school-age high.

For children under 1 year, the prevalence rate was 455 per 100,000, or about 0.5%. The estimated number living with the condition was about 46,000.

Ages 2-4 had a rate of 486 per 100,000, or about 0.5%. The count for that band was about 158,000.

The corresponding DALY measures were 23.8 per 100,000 under 1 year and 26.4 per 100,000 at ages 2-4.

Those figures create the starting point for the age comparison. They do not show a sudden high rate in the youngest band.

Age labels also matter because each band covers a different part of childhood. A child’s placement in one band changes which estimate applies.

For a reader comparing a young child with older children, the early figures sit below the rate recorded at ages 5-9.

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Ages 5-9 mark the highest listed prevalence rate

You may be focused on school age because that band carries the highest prevalence rate in this set of estimates.

Ages 5-9 recorded 569 per 100,000, or about 0.6%. The estimated number living with idiopathic developmental intellectual disability was about 340,000.

The DALY rate for ages 5-9 was 30.8 per 100,000. The total disease burden was about 18,000 DALYs.

This is the highest prevalence rate among the listed age bands. It remains close to the rates recorded later, so the difference does not create a steep age cliff.

The next band, ages 10-14, recorded 561 per 100,000, or about 0.6%. That estimate corresponds to about 354,000 people and about 19,000 DALYs.

In practical reading terms, school age marks the top of the listed prevalence pattern. The rate then eases slightly during adolescence and early adulthood.

That finding answers part of the question for a reader comparing childhood with adulthood. The later adult figures stay in the same broad range for many years.

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Ages 10-24 keep the rate near 0.6%

If your comparison reaches the teenage years or early adulthood, the recorded prevalence rate changes very little.

Ages 10-14 had a rate of 561 per 100,000, or about 0.6%. Ages 15-19 had 558 per 100,000, or about 0.6%.

Ages 20-24 recorded 556 per 100,000, or about 0.6%. The sequence moves down gradually across those three bands.

The estimated counts were about 354,000 at ages 10-14, about 357,000 at ages 15-19, and about 361,000 at ages 20-24.

The DALY totals for all three bands were about 19,000. Their DALY rates were 30.2, 29.7, and 29.5 per 100,000.

That combination matters. The prevalence rate edges down, while the estimated number of people rises across these bands.

A count and a rate answer different questions.

The count describes the estimated number in an age group, while the rate allows age groups to be compared on the same scale.

For the reader asking whether the condition disappears from the age pattern after childhood, these figures show continued presence through ages 20-24.

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Ages 25-39 form a stable adult middle

Someone checking early or middle adulthood finds the most stable part of the recorded age pattern.

Ages 25-29 had a prevalence rate of 557 per 100,000, or about 0.6%. Ages 30-34 reached 564 per 100,000, or about 0.6%.

The rate at ages 35-39 was 553 per 100,000, or about 0.6%. All three values remain close to the school-age and younger-adult rates.

Estimated counts were about 380,000 at ages 25-29, about 409,000 at ages 30-34, and about 399,000 at ages 35-39.

The matching DALY rates were 29.6, 29.9, and 29.3 per 100,000.

Total disease burden was about 20,000 at ages 25-29, about 22,000 at ages 30-34, and about 21,000 at ages 35-39.

Ages 30-34 carry the highest estimated count in the supplied age bands. That count does not mean the prevalence rate reaches a new level.

The distinction keeps the answer precise for anyone reading an adult estimate. The rate stays near 0.6%, while the estimated count varies between age bands.

Across ages 25-39, the evidence supports a stable adult middle. It does not support a sharp rise or sharp fall within those three bands.

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Ages 40-54 begin a gradual decline

When the age under review reaches the forties or early fifties, the prevalence rate begins moving below the earlier adult pattern.

Ages 40-44 recorded 538 per 100,000, or about 0.5%. Ages 45-49 recorded 516 per 100,000, or about 0.5%.

The rate at ages 50-54 was 486 per 100,000, or about 0.5%. These bands show a stepwise decline from the stable middle.

The estimated counts were about 397,000 at ages 40-44, about 371,000 at ages 45-49, and about 365,000 at ages 50-54.

DALY rates also fell across these bands, from 28.6 per 100,000 at ages 40-44 to 27.5 per 100,000 at ages 45-49 and 26 per 100,000 at ages 50-54.

The DALY totals were about 21,000 at ages 40-44, about 20,000 at ages 45-49, and about 20,000 at ages 50-54.

This part of the chart answers the age question through a slope rather than a single cutoff. The recorded rate lowers across successive bands.

For one reader trying to place an adult age, the best description is gradual change. The estimates do not identify one exact age when the pattern suddenly shifts.

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Ages 55-64 show the lowest recorded adult rates

If the age you are examining falls after 55, the GBD 2023 estimates show the lowest prevalence rates in the listed adult bands.

Ages 55-59 recorded 445 per 100,000, or about 0.4%. Ages 60-64 recorded 398 per 100,000, or about 0.4%.

The estimated number living with the condition was about 329,000 at ages 55-59 and about 281,000 at ages 60-64.

DALY rates were 23.8 per 100,000 at ages 55-59 and 21.4 per 100,000 at ages 60-64.

Total disease burden was about 18,000 and about 15,000, respectively.

The fall from the earlier adult bands continues here. The lowest listed prevalence rate appears at ages 60-64.

Those later figures should still be read as age-band estimates for high-income countries in 2023. They describe the population pattern recorded in the dataset.

They do not predict an individual person’s experience. A population estimate can place an age band in context without deciding what applies to one person.

For the reader who needs the direct age answer, later adulthood carries a lower recorded rate than school age through middle adulthood.

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How to read the age pattern for one person

You are left with three separate questions: how common the condition was, how many people were counted, and how much burden the dataset recorded.

For prevalence, the pattern rises from about 0.5% under 1 year and at ages 2-4 to about 0.6% at ages 5-9 through ages 35-39.

After that middle period, the recorded rate moves to about 0.5% at ages 40-44 through ages 50-54.

It reaches about 0.4% at ages 55-59 and ages 60-64.

For the number of people, the estimates range from about 46,000 under 1 year to about 409,000 at ages 30-34, then fall to about 281,000 at ages 60-64.

For DALYs, the age pattern reaches about 22,000 at ages 30-34 and about 15,000 at ages 60-64. The figures vary across the age bands.

The straight answer is therefore specific.

In high-income countries, GBD 2023 records a fairly steady prevalence rate from ages 5-9 through ages 35-39, followed by lower rates in later adulthood.

That conclusion describes the measured population pattern. It does not turn an age band into a personal diagnosis or a prediction.

Keep the age label, measure, year, and population together when you read any one figure. Separating those parts can change what the number appears to say.

The comparison leaves one clear message for this reader: age changes the recorded rate gradually, with the strongest downward movement appearing after the early adult years.

This is general information about the mind, not therapy or a diagnosis. If things feel hard, please consult a professional. In a crisis, reach a free, confidential crisis hotline right away; findahelpline.com lists one for your country.