Introduction: Onychocryptosis is a common and often painful nail condition, but risk factors have been relatively unexplored. We aimed to analyze associations between onychocryptosis, comorbidities, and income level. Methods: Using the National Institute of Health All of Us Research Program Database, a matched case-control study was performed for patients with onychocryptosis diagnosis and comorbidities and lifestyle factors. Results: A total of 6,246 cases of onychocryptosis and 24,984 controls were analyzed. Patients with onychocryptosis versus controls had increased risk of onychogryphosis (OR 5.66; 95% CI 4.87, 6.58), onychomycosis (2.63; 2.06, 3.36), hallux valgus (1.68; 1.50, 1.87), type 2 diabetes mellitus (1.49; 1.40, 1.60), obesity (1.38; 1.30, 1.48), and peripheral vascular disease (1.24; 1.14, 1.35) compared to controls. Patients who reported living in low-income households more often had onychocryptosis (reference group annual income >200 k; annual income <10 k USD, OR: 1.76; 95% CI: 1.46, 2.12, p < 0.001 vs. annual income 150–200 k USD, OR: 1.26; 95% CI: 0.99, 1.61, p = 0.06). Conclusion: Low income, obesity, PVD, and T2DM were associated with onychocryptosis diagnosis. It is recommended that these at-risk populations be screened for onychocryptosis and counseled on proper nail trimming techniques. Future studies are needed to examine the relationship between household income and onychocryptosis risk.

Onychocryptosis, or ingrown nail, is a common nail condition that is often painful and negatively impacts quality of life [1, 2]. Risk factors include improper nail trimming technique, pregnancy, trauma, and ill-fitting shoes [1]. The 1990 US National Health Survey reported increased frequency of onychocryptosis in individuals earning <$10,000 USD/year versus higher income respondents [3]. We aimed to analyze associations between onychocryptosis, comorbidities, and income level.

Using the National Institute of Health All of Us Research Program Database, a matched case-control study was performed for patients age ≥18 years with onychocryptosis diagnosis (Systematized Nomenclature of Medicine [SNOMED] code 400097005, Concept ID 139099). Matching 4:1 (controls: cases) was performed based on age, sex, and self-reported race/ethnicity. Using SNOMED codes, individuals were identified with hallux valgus, heart failure, hyperhidrosis, kidney disease, diabetic neuropathy, obesity, onychogryphosis, onychomycosis, osteoarthritis, peripheral vascular disease (PVD), psoriasis, type 2 diabetes mellitus (T2DM), and venous varices (Table 2). Patient survey data were used to collect annual household income. Multivariate logistic regression was performed to calculate odds ratios and p values (Table 2), with significance p < 0.05.

A total of 6,246 cases of onychocryptosis and 24,984 controls were analyzed. Mean age of onychocryptosis patients was 64.9 years old, with 62% females and 44.1% non-whites, and demographics similar to controls (all p > 0.05, Table 1). Patients with onychocryptosis versus controls had increased risk of onychogryphosis (OR: 5.66; 95% CI: 4.87, 6.58), onychomycosis (2.63; 2.06, 3.36), hallux valgus (1.68; 1.50, 1.87), T2DM (1.49; 1.40, 1.60), obesity (1.38; 1.30, 1.48), and PVD (1.24; 1.14, 1.35) compared to controls (all p < 0.05) (Table 2). Patients who reported living in low-income households more often had onychocryptosis (reference group annual income >200 k; annual income <10 k USD, OR: 1.76; 95% CI: 1.46, 2.12, p < 0.001 vs. annual income 150–200 k USD, OR: 1.26; 95% CI: 0.99, 1.61, p = 0.06) (Table 2).

Table 1.

Demographic characteristics of individuals with onychocryptosis and controls matched on age, sex, and self-reported race/ethnicity

Matched controls (n = 24,984)Melasma (n = 6,246)p value
Age, mean (std) 64.9 (14.18) 64.9 (14.19) 0.9873 
Sex at birth count (%)   
 Male 9,232 (37.9) 2,308 (37.9)  
 Female 15,132 (62.1) 3,783 (62.1)  
Self-reported race/ethnicity count (%)   
 White 13,964 (55.9) 3,491 (55.9)  
 Black or African American 5,008 (20.0) 1,252 (20.0)  
 Hispanic or Latino 4,352 (17.4) 1,088 (17.4)  
 Asian 192 (0.77) 48 (0.77)  
 Other 1,468 (5.9) 367 (5.9)  
Matched controls (n = 24,984)Melasma (n = 6,246)p value
Age, mean (std) 64.9 (14.18) 64.9 (14.19) 0.9873 
Sex at birth count (%)   
 Male 9,232 (37.9) 2,308 (37.9)  
 Female 15,132 (62.1) 3,783 (62.1)  
Self-reported race/ethnicity count (%)   
 White 13,964 (55.9) 3,491 (55.9)  
 Black or African American 5,008 (20.0) 1,252 (20.0)  
 Hispanic or Latino 4,352 (17.4) 1,088 (17.4)  
 Asian 192 (0.77) 48 (0.77)  
 Other 1,468 (5.9) 367 (5.9)  
Table 2.

Association of onychocryptosis with co-morbidities and lifestyle risk factors for disease

Comorbidity or lifestyle factorSNOMEDControls (n = 24,984), n (%)Onychocryptosis (n = 6,246), n (%)OR [95% CI]p value
PVD 400047006 2,766 (11.1) 1,140 (18.3) 1.24 [1.14, 1.35] <0.001 
Diabetic neuropathy 230572002 160 (0.6) 124 (2.0) 1.30 [0.99, 1.70] 0.064 
Onychomycosis 414941008 194 (0.8) 130 (2.1) 2.63 [2.06, 3.36] <0.001 
Hallux valgus 415692008, 122480009 1,331 (5.3) 645 (10.3) 1.68 [1.50, 1.87] <0.001 
Kidney disease 90708001 761 (3.0) 341 (5.5) 0.99 [0.85, 1.15] 0.87 
Hyperhidrosis 312230002 40 (0.2) ≤20* 1.13 [0.56, 2.31] 0.73 
Psoriasis 9014002 1,545 (6.2) 463 (7.4) 1.03 [0.92, 1.17] 0.58 
Venous varices 128060009 1,201 (4.8) 420 (6.7) 1.03 [0.90, 1.17] 0.70 
Heart failure 84114007 3,097 (12.4) 874 (14.0) 0.79 [0.72, 0.87] <0.001 
Osteoarthritis 396275006 10,058 (40.3) 2,877 (46.1) 0.97 [0.91, 1.03] 0.31 
Onychogryphosis 952897009 326 (1.3) 606 (9.7) 5.66 [4.87, 6.58] <0.001 
T2DM 44054006 5,023 (20.1) 2,210 (35.4) 1.49 [1.40, 1.60] <0.001 
Obesity 414916001 14,702 (58.8) 4,294 (68.7) 1.38 [1.30, 1.48] <0.001 
Annual income >200 k Concept ID 1585375 1,161 (4.6) 174 (2.8) 1 (ref) 
Annual income 150–200 k USD Concept ID 1585375 878 (3.5) 158 (2.5) 1.26 [0.99, 1.61] 0.06 
Annual income 100 k–150 k USD Concept ID 1585375 2,195 (8.8) 438 (7.0) 1.26 [1.03, 1.54] <0.05 
Annual income 75 k–100 k USD Concept ID 1585375 1,919 (7.7) 483 (7.7) 1.52 [1.24, 1.85] <0.001 
Annual income 50 k–75 k USD Concept ID 1585375 2,729 (10.9) 712 (11.4) 1.51 [1.25, 1.83] <0.001 
Annual income 35 k–50 k USD Concept ID 1585375 2,045 (8.2) 580 (9.3) 1.63 [1.34, 1.98] <0.001 
Annual income 25 k–35 k USD Concept ID 1585375 1,875 (7.5) 504 (8.1) 1.63 [1.34, 1.99] <0.001 
Annual income 10 k–25 k USD Concept ID 1585375 3,443 (13.8) 1,026 (16.4) 1.70 [1.41, 2.04] <0.001 
Annual income <10 k USD Concept ID 1585375 3,085 (12.3) 848 (13.6) 1.76 [1.46, 2.12] <0.001 
Comorbidity or lifestyle factorSNOMEDControls (n = 24,984), n (%)Onychocryptosis (n = 6,246), n (%)OR [95% CI]p value
PVD 400047006 2,766 (11.1) 1,140 (18.3) 1.24 [1.14, 1.35] <0.001 
Diabetic neuropathy 230572002 160 (0.6) 124 (2.0) 1.30 [0.99, 1.70] 0.064 
Onychomycosis 414941008 194 (0.8) 130 (2.1) 2.63 [2.06, 3.36] <0.001 
Hallux valgus 415692008, 122480009 1,331 (5.3) 645 (10.3) 1.68 [1.50, 1.87] <0.001 
Kidney disease 90708001 761 (3.0) 341 (5.5) 0.99 [0.85, 1.15] 0.87 
Hyperhidrosis 312230002 40 (0.2) ≤20* 1.13 [0.56, 2.31] 0.73 
Psoriasis 9014002 1,545 (6.2) 463 (7.4) 1.03 [0.92, 1.17] 0.58 
Venous varices 128060009 1,201 (4.8) 420 (6.7) 1.03 [0.90, 1.17] 0.70 
Heart failure 84114007 3,097 (12.4) 874 (14.0) 0.79 [0.72, 0.87] <0.001 
Osteoarthritis 396275006 10,058 (40.3) 2,877 (46.1) 0.97 [0.91, 1.03] 0.31 
Onychogryphosis 952897009 326 (1.3) 606 (9.7) 5.66 [4.87, 6.58] <0.001 
T2DM 44054006 5,023 (20.1) 2,210 (35.4) 1.49 [1.40, 1.60] <0.001 
Obesity 414916001 14,702 (58.8) 4,294 (68.7) 1.38 [1.30, 1.48] <0.001 
Annual income >200 k Concept ID 1585375 1,161 (4.6) 174 (2.8) 1 (ref) 
Annual income 150–200 k USD Concept ID 1585375 878 (3.5) 158 (2.5) 1.26 [0.99, 1.61] 0.06 
Annual income 100 k–150 k USD Concept ID 1585375 2,195 (8.8) 438 (7.0) 1.26 [1.03, 1.54] <0.05 
Annual income 75 k–100 k USD Concept ID 1585375 1,919 (7.7) 483 (7.7) 1.52 [1.24, 1.85] <0.001 
Annual income 50 k–75 k USD Concept ID 1585375 2,729 (10.9) 712 (11.4) 1.51 [1.25, 1.83] <0.001 
Annual income 35 k–50 k USD Concept ID 1585375 2,045 (8.2) 580 (9.3) 1.63 [1.34, 1.98] <0.001 
Annual income 25 k–35 k USD Concept ID 1585375 1,875 (7.5) 504 (8.1) 1.63 [1.34, 1.99] <0.001 
Annual income 10 k–25 k USD Concept ID 1585375 3,443 (13.8) 1,026 (16.4) 1.70 [1.41, 2.04] <0.001 
Annual income <10 k USD Concept ID 1585375 3,085 (12.3) 848 (13.6) 1.76 [1.46, 2.12] <0.001 

Patients from lower versus higher income households more often had a co-diagnosis of onychocryptosis, similar to findings from the 1990 US National Health Survey. This association is likely multifactorial, including decreased access of lower income households to medical care and less income to purchase proper fitting shoes or nail grooming tools [3]. We showed that onychocryptosis is positively correlated with obesity, similar to a retrospective study of 206 patients with 729 ingrown nails, with 34.1% of patients having obesity as a co-diagnosis [2]. Low socioeconomic status is a risk factor for obesity, which may contribute to this association. In a 5-year longitudinal cohort study of students aged 11-12 years old, females in the lowest one-fifth versus higher four-fifths of residential areas by socioeconomic status had higher obesity rates (all p < 0.001) [4]. While these associations are correlative and not necessarily causal, obesity may increase foot constriction while wearing shoes or place increased pressure on the lower extremities, leading to onychocryptosis.

We also found that PVD and T2DM were associated with onychocryptosis, which may be explained by altered walking mechanics and increased trauma risk due to impaired muscle strength, decreased sensation, or increased lower extremity edema resulting from these conditions [1]. Onychomycosis and onychogryphosis were also associated with onychocryptosis, potentially due to onychodystrophy that occurs secondary to these nail diseases [5]. Limitations include lack of information about onychocryptosis treatment and number of nails involved and potential for miscoding.

In sum, we found that patients from low-income versus higher income households were more often diagnosed with onychocryptosis and identified several important comorbidities. Patients with these comorbidities can be counseled on their increased likelihood of developing onychocryptosis, and dermatologists and podiatrists play an important role in educating patients on proper nail care techniques. Future studies are needed to explore the relationship between household income and onychocryptosis risk to identify opportunities for intervention in low-income communities.

The All of Us Research Program is supported by the National Institutes of Health, Office of the Director: Regional Medical Centers: 1 OT2 OD026549; 1 OT2 OD026554; 1 OT2 OD026557; 1 OT2 OD026556; 1 OT2 OD026550; 1 OT2 OD 026552; 1 OT2 OD026553; 1 OT2 OD026548; 1 OT2 OD026551; 1 OT2 OD026555; and IAA #: AOD 16037; Federally Qualified Health Centers: HHSN 263201600085U; Data and Research Center: 5 U2C OD023196; Biobank: 1 U24 OD023121; the Participant Center: U24 OD023176; Participant Technology Systems Center: 1 U24 OD023163; Communications and Engagement: 3 OT2 OD023205 and 3 OT2 OD023206; and Community Partners: 1 OT2 OD025277; 3 OT2 OD025315; 1 OT2 OD025337; and 1 OT2 OD025276. In addition, the All of Us Research Program would not be possible without the partnership of its participants. We gratefully acknowledge All of Us participants for their contributions, without whom this research would not have been possible. We also thank the National Institutes of Health’s All of Us Research Program for making available the participant data examined in this study.

Per the All of Us Research Hub at the National Institutes of Health: “as a single IRB, the All of Us IRB is charged with reviewing the protocol, informed consent, and other participant-facing materials for the All of Us Research Program. The IRB follows the regulations and guidance of the Office for Human Research Protections for all studies, ensuring that the rights and welfare of research participants are overseen and protected uniformly. The Researcher Workbench employs a data passport model, through which authorized users do not need IRB review for each research project. Most authorized users will not be conducting human subjects research with All of Us data for two reasons: (1) The research will not directly involve participants, only their data, and (2) the data available in the Researcher Workbench have been carefully checked and altered to remove identifying information while preserving their scientific utility.” This study protocol was reviewed and the need for informed consent was waived by Weill Cornell Medicine Human Research Compliance.

The authors have no conflicts of interest relevant to the content of this article.

No specific funding was received from any bodies in the public, commercial, or not-for-profit sectors to carry out the work described in this article.

Rachel Hill prepared methodology, acquired and interpreted data for the work, wrote the original manuscript draft, prepared tables, gave final consent for the version to be published, and agreed to be accountable for all aspects of the work. Mr. Onajia Stubblefield and Tracey Vlahovic acquired and interpreted data for the work, gave final consent for the version to be published, and agreed to be accountable for all aspects of the work. Shari Lipner conceptualized the work, prepared methodology, acquired and interpreted data for the work, reviewed and edited the manuscript, gave final consent for the version to be published, and agreed to be accountable for all aspects of the work.

The authors confirm that the data supporting the findings of this study are available within the article. Further inquiries can be directed to the corresponding author.

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