Hair type changes significantly with age. The hair that grows from the scalp in adulthood is often noticeably different in texture, density, and color than the hair of youth. These shifts are a natural outcome of biological processes occurring deep within the hair follicle. Hair aging involves changes in genetic signaling, hormonal balances, and the accumulation of damage over a lifetime.
The Role of Hormones and Genetics in Follicle Shape
The fundamental characteristic of hair texture—whether it is straight, wavy, or curly—is determined by the shape of the hair follicle itself. A follicle with a perfectly round cross-section produces straight hair, while an increasingly oval or flattened shape leads to curlier textures. This follicular shape is primarily dictated by genetics, but it is heavily influenced by hormonal signals throughout life.
Major hormonal fluctuations, such as those experienced during puberty, pregnancy, or menopause, can trigger changes in the expression of genes that regulate follicle structure. For instance, a rise in androgens relative to estrogen can affect the hair follicle, sometimes causing previously straight hair to become wavier or curlier. Conversely, a drop in estrogen, particularly after menopause, can also alter the follicle, sometimes leading to hair that feels coarser or more brittle.
These shifts mean that the hair growth cycle begins to produce strands with a subtly or dramatically different configuration, reflecting the current hormonal environment. This leads to permanent texture changes in the new hair growth.
Visible Structural Changes: Color, Density, and Texture
The most widely recognized sign of hair aging is the loss of color, known as graying. This occurs because the melanocytes, the specialized cells producing the pigment melanin, gradually decrease their activity over time. Eventually, these cells stop injecting pigment into the hair shaft entirely, causing the new hair to grow out clear, which appears white or gray against pigmented strands. The timing of this process is largely controlled by genetics.
Hair density and volume also change significantly with age due to a phenomenon called follicular miniaturization. This process, often driven by genetic sensitivity to the hormone dihydrotestosterone (DHT), causes hair follicles to gradually shrink. As the follicle miniaturizes, the active growth phase, known as anagen, becomes progressively shorter. This results in the production of shorter, finer, and thinner hairs over successive growth cycles.
This miniaturization leads to reduced hair density across the scalp, which is the biological basis for pattern hair thinning in both men and women. Beyond density, the texture of individual strands alters, with the hair shaft diameter typically decreasing starting around the fourth decade of life. Finer hair is less resilient and more susceptible to damage.
Furthermore, the scalp’s sebaceous glands produce less sebum, the natural oil that lubricates the hair shaft, as a person ages. This reduction in natural conditioning leaves the hair drier and more prone to brittleness. The combination of a reduced diameter and decreased moisture contributes to a wiry or coarse feel, even in hair that was once soft and pliable.
External Factors Influencing Hair Aging
While internal biology drives most age-related changes, external factors act as modifiers, influencing the speed and severity of hair aging. Environmental stressors, such as chronic exposure to ultraviolet (UV) radiation from the sun, induce oxidative stress on the hair and scalp. This damage can degrade the hair shaft’s protein structure, leading to a loss of strength, shine, and color.
Exposure to air pollution and other environmental toxins also contributes to oxidative stress, potentially disrupting the normal function of the hair follicle. Over decades, repeated chemical treatments, excessive heat styling, and harsh grooming practices also accumulate damage, making the hair more fragile and less able to withstand natural aging processes. This weathering exacerbates the natural decrease in hair resilience that comes with age.
Lifestyle factors play an important role, with chronic psychological stress impacting the hair growth cycle. Sustained high levels of cortisol, a stress hormone, can disrupt the balance of the hair cycle phases, sometimes accelerating shedding. Additionally, the quantity and quality of hair are closely linked to nutritional status. Deficiencies in essential nutrients like proteins, trace elements, and vitamins can impair the hair follicle’s ability to grow and maintain pigmentation, accelerating the visible signs of aging.