Does Head Circumference Decrease with Age? The Reality of Adult Cranial Changes
Many people assume that as we get older, our entire body, including our skull, shrinks. While a person's height may decrease due to spinal changes like compressed discs and bone loss in the vertebrae, the skull's bone structure and soft tissue behave differently. The common notion that your head gets smaller is largely a myth. Here's a deeper look into the physiological changes that actually occur as we age.
Brain Volume Decreases While Skull Size Stays Stable
One of the most surprising findings about aging and the head is the contrasting fate of the brain and the skull. Starting in adulthood, the brain begins a process of atrophy, or gradual volume loss. This process accelerates in later decades and is more pronounced in individuals with neurodegenerative diseases like Alzheimer's.
Interestingly, this brain atrophy does not cause the head to shrink. The skull itself is largely a fixed structure by early adulthood, with the cranial sutures (the fibrous joints between the skull bones) fused together by around age 20. The space created by the shrinking brain is often filled with cerebrospinal fluid, meaning the overall intracranial volume (the space inside the skull) does not decrease enough to cause an external change in head circumference.
The Complexities of Bone Remodeling
While the main skull structure is set, the bones still undergo a process called remodeling throughout life. This involves a continuous cycle of old bone resorption and new bone formation. Studies have revealed that this remodeling process can manifest differently in older adults:
- Internal thickening: Some research shows a thickening of the inner table of the skull, particularly in the frontal region, a phenomenon more pronounced in women. This inner thickening reduces the overall volume of the intracranial space but does not affect the external circumference measurement.
- Outer expansion: At the same time, the outer table can experience slight expansion. Some studies have noted subtle, continuous growth rates in certain head dimensions throughout adulthood, though these are typically minor.
- Facial bone changes: The facial skeleton also changes with age. Bones in areas like the orbits (eye sockets), maxilla (upper jaw), and mandible (lower jaw) can resorb in specific locations, which contributes to an aged appearance and changes in facial structure.
Factors Influencing Perceived Head Size
Even without a decrease in head circumference, several non-skeletal factors can affect how a person perceives their head size, or how it is measured over time:
- Weight fluctuations: Significant weight gain can lead to increased fat deposits in the scalp, neck, and facial regions, which can add to overall head circumference and make a hat feel tighter. Conversely, weight loss may cause a perceived decrease.
- Fluid retention: Conditions causing fluid retention (edema), such as certain medications or health issues like thyroid disorders, can cause swelling in the soft tissues of the face and scalp.
- Changes in skin and muscle: Aging causes skin to lose elasticity and fat pads in the face to shift. These soft tissue changes can alter facial proportions and contour, which might create the illusion of a differently sized head.
- Hair loss: Thinning hair or a receding hairline can expose more of the scalp, creating an optical illusion that makes the head appear larger or longer than it did when hair was thick.
Normal Aging vs. Abnormal Growth: A Comparison
| Feature | Normal Aging Changes | Abnormal Head Changes |
|---|---|---|
| Head Circumference | Generally stable, though slight increases may occur due to mild bone remodeling or weight gain. | Rapid or significant increase (e.g., several centimeters) warrants medical investigation. |
| Brain Volume | Gradual, non-significant decrease (atrophy) from adolescence onward. | Marked or rapid brain atrophy, often associated with cognitive decline. |
| Skull Structure | Inner table thickening (particularly in females), subtle outer remodeling of cranial and facial bones. | Gross enlargement and malformation of bones due to conditions like Paget's disease or acromegaly. |
| Cognitive Function | Cognitive ability is generally preserved in healthy aging, but brain changes related to disease can affect function. | Severe cognitive impairment linked to smaller head circumference or disease-related atrophy. |
| Soft Tissue | Shifting facial fat pads, loss of skin elasticity, which alters facial proportions and perception of head size. | Significant facial swelling (edema) linked to systemic diseases such as thyroid disorders. |
Conclusion
Contrary to the widely held assumption, head circumference does not typically decrease with age. The primary cranial bones fuse in early adulthood, setting the outer dimensions of the skull for life. While the brain undergoes a natural and gradual process of volume reduction (atrophy), the skull compensates by filling the intracranial space with cerebrospinal fluid or thickening its inner wall, thus maintaining its external size. The perception of a changing head size can often be attributed to more common age-related factors, such as weight fluctuations, hormonal shifts, and alterations in the facial soft tissues. While these changes are normal, any significant or rapid change in head size or shape accompanied by other symptoms should be evaluated by a healthcare professional to rule out rare underlying medical conditions.
For more detailed information, the American Academy of Facial Esthetics provides additional context on the various factors contributing to facial aging, including bone and soft tissue changes.
