Smoking Associated with Increased Nail Psoriasis Severity, Case-Control Study Finds

A recent case-control study has found that smoking is associated with more severe nail psoriasis, adding to growing evidence that lifestyle factors may influence disease burden in this patient population.¹ Although smoking was not associated with greater overall psoriasis severity or a higher prevalence of psoriatic arthritis, smokers with nail psoriasis had significantly higher Nail Psoriasis Severity Index (NAPSI) scores than nonsmokers.

Study Background and Objectives

The relationship between smoking and nail involvement has received comparatively little attention despite the substantial impact nail psoriasis can have on quality of life and daily functioning. The study enrolled 218 patients with psoriasis and 218 age- and sex-matched controls between January and November 2023 at Razi and Imam Khomeini Hospitals in Tehran, Iran. Diagnoses were confirmed by board-certified dermatologists and histopathologic examination. Researchers collected participants' smoking histories, including smoking duration and cigarettes smoked per day, and assessed disease severity using the Psoriasis Area and Severity Index (PASI) and nail involvement using the NAPSI.

Smoking was significantly more common among patients with psoriasis than among controls. More than one-quarter of patients (27.5%) were current smokers compared with 6.0% of controls (P < .001). Patients with psoriasis also reported significantly longer smoking histories than controls, averaging 18.9 years versus 4.4 years (P < .001). Although psoriasis patients smoked more cigarettes per day on average than controls, this difference was not statistically significant.

Nail Severity vs. Overall Disease Burden

Among patients with psoriasis, smoking was associated with significantly greater nail disease severity. Current smokers had a mean NAPSI score of 23.8 ± 18.6 compared with 12.3 ± 11.2 among nonsmokers (P = .001), indicating substantially more severe nail involvement. In contrast, smoking did not appear to influence overall skin disease severity. Mean PASI scores were similar between smokers and nonsmokers (4.83 vs 5.14, respectively; P = .76). Likewise, the prevalence of psoriatic arthritis did not differ significantly, occurring in 13.3% of smokers and 12.7% of nonsmokers (P = .894).

Overall, nail involvement was present in 110 of the 218 patients with psoriasis. Investigators found no significant differences between patients with and without nail psoriasis in age, sex, body mass index, psoriasis duration, PASI score, or treatment type. Smoking prevalence was numerically higher among patients with nail involvement (31.8%) than among those without nail disease (23.1%), but the difference did not reach statistical significance.

Similarly, smoking duration and the number of cigarettes smoked per day were not significantly associated with the presence of nail involvement. Patients with nail psoriasis had smoked for an average of 22 years compared with 15 years among those without nail disease, but this difference was not statistically significant. Daily cigarette consumption also did not differ significantly between groups.

Lifestyle Factors and Potential Mechanisms

The study also found no association between obesity and nail involvement, despite obesity's recognized role as a risk factor for psoriasis overall. Investigators noted that lifestyle interventions extending beyond pharmacologic treatment, including smoking cessation, weight management, and reduced alcohol consumption, may contribute to improved overall health in patients with psoriasis while also addressing cardiovascular risk factors.

The investigators noted that their findings align with previous research linking smoking to psoriasis while further supporting an association between smoking and more severe nail disease.² They suggested that smoking may contribute to nail psoriasis through multiple mechanisms, including oxidative stress, inflammatory signaling, vascular changes affecting the nail matrix, and local trauma that may promote psoriatic lesions.

Study Limitations and Future Directions

Because nail psoriasis can be difficult to treat and often has a substantial impact on patients' quality of life, addressing modifiable risk factors such as smoking may be an important component of comprehensive psoriasis management.

“These findings emphasize the importance of screening psoriasis patients for smoking habits and supporting public health efforts to encourage quitting smoking, which may lower the chance of getting psoriasis,” the authors wrote.

The researchers did acknowledge several limitations, including the study's cross-sectional design, which precluded assessment of the long-term effects of smoking or smoking cessation on nail psoriasis. Additional limitations included reliance on self-reported smoking histories and the inability to fully account for all potential comorbidities. Prospective longitudinal studies are needed to determine whether smoking cessation can reduce the development or severity of nail psoriasis.

References

1. Shakoei S, Heidari F, Nasimi M, et al. Smoking and Nail Psoriasis: Examining the Connection in a Case-Control Study. Dermatol Ther. 2026, 9055487, 6 pages, 2026. doi:10.1155/dth/9055487

2. Temiz SA, Özer İ, Ataseven A, Dursun R, Uyar M. The effect of smoking on the psoriasis: Is it related to nail involvement?. Dermatol Ther. 2020;33(6):e13960. doi:10.1111/dth.13960