This retrospective cohort study explored clinical factors associated with graded clinical improvement in atrophic acne scars treated using FL and FRF. Utilizing a multivariable ordinal logistic regression model, we found that older age, male sex, shorter scar duration, lower Fitzpatrick skin phototypes, and completing at least three treatment sessions were independently associated with greater clinical improvement. Notably, among patients with severe to very severe scarring, completing a minimum of three treatment sessions significantly improved outcomes, underscoring the importance of treatment intensity in managing advanced scarring.

In the multivariable analysis, older age was consistently associated with greater clinical improvement, a finding that aligns with previous studies suggesting better compliance and more realistic expectations in older individuals. Apart from these deleterious aspects, elderly healing presents some advantages. Pathological scarring, including hypertrophic scars and/or keloids, is uncommon in the elderly because of a reduction in inflammation. In aged patients, skin laxity generally facilitates easy reapproximation of the edges, allowing for tension-free suturing and resulting in favorable scarring outcomes [25]. This may also reflect age-related hormonal stabilization, leading to a more favorable microenvironment for collagen remodeling. Fang et al. similarly demonstrated that older patients exhibited better responses to ablative fractional CO2 laser treatments in Asian populations [26]. Zou et al. also found that age was not a limiting factor for successful treatment outcomes using ablative laser [27]. However, Miao et al. suggested that younger patients, due to higher collagen metabolism, might respond better to regenerative therapies, indicating that age-related responses could vary depending on treatment modalities [28].

The anatomical and physiological differences of male skin have significant consequences for the application of lasers and energy-based devices. It is denser than female skin because of variations in the response to and management of sex hormones [29]. Male sex was independently associated with greater clinical improvement, likely because of higher collagen density and thicker dermis in male skin, favoring neocollagenesis [14]. Moreover, male individuals typically recover faster than their female counterparts following face cosmetic laser treatments, perhaps due to a greater density of hair follicles [30]. Yeung et al. reported that male patients showed significant improvement after combined fractional radiofrequency and laser treatments, supporting the hypothesis that male skin may respond more robustly to EBDs [14].

The Fitzpatrick skin classification is frequently used to categorize skin into six grades (I–VI) based on its response to UV light, which is inversely proportional to its melanin content. In particular, types IV and VI present a darker skin color and a higher melanin content. The epidermis absorbs a broader range of light energy, resulting in a relatively higher amount of heat production. This condition has the potential to impede the depth of laser penetration and impact its efficacy [31]. In our study, we found that a higher Fitzpatrick skin type was negatively correlated with clinical improvement, consistent with prior studies indicating that melanin-rich skin absorbs more superficial laser energy, limiting deeper dermal penetration necessary for effective collagen remodeling [28]. During practice, physicians take caution when adjusting laser parameters to prevent skin damage from excessive melanin absorption, although higher energy levels may be recommended [13]. Additionally, the increased risk of PIH in darker skin types often leads to the use of lower energy settings, further reducing treatment efficacy [28].

Deciding when to start laser therapy can be difficult because of the diversity in the literature. This variability may arise from differences in study designs, patient populations, and treatment protocols, making it difficult for clinicians to establish a standardized approach. We discovered a negative correlation between increasing scar age and clinical improvement. Shorter scar duration was another positive predictor of improvement. The optimal timeframe for laser therapy was previously believed to be when the scar had fully matured. Nevertheless, recent research has indicated a correlation between early initiation and the reduction in symptoms, contractures, improvement in mobility, and the overall rehabilitation process [32, 33]. Early treatment may be more effective because immature scars have more active fibroblasts and ongoing collagen remodeling. In contrast, mature scars become fibrotic and less responsive to interventions [34]. We found that laser intervention has the potential to alter the wound healing phases, which could subsequently influence scar formation. Subgroup analysis showed different results between treatment modalities. In the FL group, older age and shorter scar duration predicted better outcomes, but patients with mixed scar types had lower improvement—possibly due to the laser’s limited ability to treat different scar morphologies effectively [26]. In the FRF group, only older age remained significant. The microneedle-based FRF device delivers energy directly into the dermis, helping to improve scars regardless of type and minimizing PIH risk, which is important for patients with darker skin tones [14].

A notable finding was that completing at least three treatment sessions significantly improved clinical outcomes among patients with severe to very severe scarring. These findings align with panel recommendations for FL in acne scar treatment, which indicate that the majority (95%) of panelists anticipate performing a series of two to four ablative fractional laser sessions to achieve a satisfactory clinical response. Similarly, the average number of FRF treatments required for optimal improvement of atrophic acne scars ranges from four to eight. Additionally, 86% of respondents highlighted the necessity of three to six treatment sessions when using fractional picosecond laser technology [9]. This supports the concept of cumulative dermal remodeling, where repeated fractional injury stimulates collagen deposition and extracellular matrix reorganization over time [32, 33]. Patients with mild to moderate scarring did not exhibit this effect, indicating that fewer treatment sessions might be sufficient for less severe cases.

A key strength of this study is the use of a graded clinical improvement outcome rather than a binary assessment. This provides a more nuanced evaluation of treatment effects, facilitating clearer interpretation and comparability across studies. Future research should adopt similar outcome measures to ensure consistency and improve clinical applicability. Prospective, multicenter studies are needed to validate these prognostic factors across diverse populations and EBD platforms. Future research should also incorporate histological analyses and patient-reported outcome measures to better understand the biological mechanisms underlying treatment responses and develop precision-based therapeutic strategies.

This study has several limitations. First, its retrospective design may introduce selection and information biases; however, these risks were minimized through strict inclusion criteria and exclusion of incomplete records. Moreover, this limitation was addressed by performing sensitivity analyses, which consistently demonstrated the robustness of the results across all analytical approaches. Second, the single-center nature limits generalizability. Third, only two EBD modalities—FL and FRF—were evaluated; thus, the results may not be applicable to other technologies or modalities. Finally, clinical improvement in our study was evaluated using standardized, physician-graded photographic assessments. However, the absence of objective imaging modalities (e.g., high-frequency ultrasound or optical coherence tomography) and histopathological confirmation limits the ability to validate dermal remodeling or scar depth improvement. Additionally, patient-reported outcome measures (PROMs), such as satisfaction, discomfort, or quality of life changes, were not assessed because of the retrospective nature of the data. Future prospective studies should incorporate both objective imaging and validated PROMs to provide a more comprehensive and patient-centered evaluation of treatment efficacy.