Changes in brain weights during the span of human life: relation of brain weights to body heights and body weights.
Level 4 - case-series / case-control
Retrospective cross-sectional autopsy series
PubMed 727739 · doi:10.1002/ana.410040410
What was done
Researchers surveyed more than 20,000 autopsy reports from several general hospitals to select fresh, non-pathological brains. A cohort of 2,773 males and 1,963 females (total n = 4,736) with documented body weight, body height, and cause of death was stratified into 23 age groups ranging from birth to 86+ years to evaluate brain weight changes across the lifespan.
What was found
Male brains were 9.8% heavier overall than female brains. In both sexes, brain weight quadrupled from birth values within the first 3 years of life and barely quintupled over the subsequent 15 years, peaking at approximately 19 years of age. A progressive decline began at approximately 45 to 50 years of age, resulting in an approximate 11% reduction in mean brain weight after age 86 compared to peak young adult weight. Differential rates of change in brain weight relative to body height and weight were observed across age groups and were less affected by sex.
Why it matters
This study provides normative reference curves for postmortem human brain growth and aging-related decline relative to body size across the human lifespan.
Limits
The cross-sectional autopsy design cannot capture individual longitudinal trajectories and may be confounded by secular cohort trends in height and body mass. Hospital autopsy cases may introduce selection bias.
Cited by
- supports The human brain weighs approximately three pounds.