Hello, I'm Dr. Yoosuk Chung, plastic surgeon at The line Plastic Surgery.
I've kept up with skincare, so why does sagging continue?
many patients ask, "I've been consistent with skincare and firming products — why does sagging keep progressing?" Since skin is what we see, it's natural to assume sagging is purely a skin issue. But in consultations, patients often get confused when a term like "SMAS" comes up — an unfamiliar layer they've never heard of.
To get straight to the point: sagging isn't explained by declining skin (dermal) elasticity alone. Just beneath the skin lies a separate fibrous tissue layer called the SMAS (superficial musculoaponeurotic system), and research shows that this layer thins and loosens at its own pace, independent of skin aging. In other words, firming creams and home skincare generally only reach the dermis — they don't affect changes happening in the SMAS layer beneath it. If it feels like your efforts aren't paying off, it may not be a lack of effort — it may be a change occurring outside the reach of skincare altogether.
What exactly is the SMAS?
The face is commonly described as having five layers. From the surface inward: skin, subcutaneous fat, SMAS, a sub-fascial gliding layer, and the periosteum covering the bone. The SMAS is a fibrous membrane that envelops the muscles responsible for facial expression, made up of interwoven muscle fibers, collagen fibers, and elastic fibers[1].
Think of the face like a garment: the skin is the outer fabric, and the SMAS is more like the inner lining that holds its shape. Even if the outer fabric still looks fine, if the inner lining loses structure first, the whole silhouette can collapse — similarly, skin can look relatively firm while the SMAS underneath is already thinning.
Is there evidence that skin and SMAS age separately?
A study measured SMAS thickness directly via CT scan in 100 Japanese women aged 20 to 79[2]. The study found SMAS thickness was significantly lower in older age groups, with the 60-79 group measuring thinner than even the 40-59 group[2]. Interestingly, no statistically significant correlation was found between SMAS thickness and body mass index(BMI)[2] — meaning the SMAS appears to thin independently with age, regardless of weight gain or loss.
Research on skin tells a similar story. A study analyzing skin tissue layer by layer found that within the dermis itself, the papillary layer closer to the surface begins losing mechanical integrity earlier than the deeper reticular layer[3]. In other words, even within the skin alone, not all layers age at the same rate — collagen and elastin content decline on different timelines depending on the layer[3].
in summary, sagging is less a simple "skin versus SMAS" issue and more the cumulative result of multiple layers aging at their own, different rate. These studies suggest that while skincare can help maintain the dermis, it doesn't extend to changes happening in the SMAS layer beneath it.
Individual variation and things to keep in mind
Which ages faster or more noticeably— the skin or the SMAS —can vary from person to person.
The rate of difference between layers can vary based on age, weight changes, genetic factors, and hormonal status.
The studies cited above measured anatomical changes by layer; they are not clinical trials directly testing the effectiveness of any specific procedure.
Which layer is more responsible for you own sagging is best confirmed through an in-person consultation with a specialist.
Three key takeaways
1. Facial sagging isn't explained by declining skin (dermal) elasticity alone — changes in the SMAS layer beneath the skin also play a separate role.
2. A CT-based study found SMAS thickness decreases significantly with age but shows no relationship with BMI, suggesting it's a separate aging process independent of body weight[2].
3. Even within the skin, different layers age at different rates, meaning sagging results from multiple layers changing at their own pace rather than a simple skin-versus-SMAS divide[3].
Which layer is behind your sagging is best confirmed through an in-person consultation with a specialist.
By Dr. Yoosuk Chung (Board-Certified Plastic Surgeon)
--- Sources
1. Anatomy, Skin, Superficial Musculoaponeurotic System (SMAS) Fascia. StatPearls, NCBI Bookshelf. NCBI Bookshelf
2. Okuda I, Abe K, Yoshioka N, et al. Objective Analysis of Age-Related Changes in the Superficial Musculoaponeurotic System in Japanese Females Using Computed Tomography. Aesthet Surg J Open Forum. 2023. PMC 10270653
3. A mechanistic view on the aging human skin through ex vivo layer-by-layer analysis of mechanics and microstructure of facial and mammary dermis. Sci Rep. 2022. Nature Scientific Reports
This article summarizes questions around facial sagging and the SMAS based on research published on PubMed and in academic journals. Please consult a specialist to confirm your individual condition.