Does tattooing benefit the immune system? The inking of immunity.

Methods

Summary

We will conduct our research at the Northwest Tatau Festival, Seattle-Tacoma WA (June 29-30, 2018) using methodology developed and tested during our two preliminary studies.

Our goal is to recruit at least 100 participants for this study. This sample size is estimated using G*Power to detect at least a moderate statistical effect (f² = .25, α = .05) of tattoo experience on the difference in IgA from pre-post tattoo in a model with ten predictors.

After participants are consented, they will be given a questionnaire to collect information on participant age, gender, perceived stress, perceived social status, and previous tattoo experience. Previous tattoo experience is indicated by percentage body coverage, year, and number of hours each tattoo took. Body coverage is determined using a body outline with an overlaid grid. The researcher fills in the tattoo coverage and the PBC is calculated. Start and end time of tattoo will be used as an additional control.

Body composition impacts immune response and will be controlled for in analysis with participant height, weight, percentile fat (bioimpedance analyzer), and handgrip strength (hand dynamometer) are collected.

Two saliva samples (1.8mL each) will be collected to measure immune functioning (IgA), and stress (cortisol). The first sample is collected directly before the tattoo begins, the second right after the tattoo concludes. A subset of 25 participants will provide samples upon waking and every 30 minutes throughout the day they receive tattoos. Assays will be conducted following protocols developed by immunologist and team member Michael Muehlenbein, Director of the Laboratory for Evolutionary Medicine at Baylor University (https://michaelmuehlenbein.org...).  

We will use theoretical and statistical means to develop an appropriate predictive model. Statistical analysis will involve, for instance, repeated measures analysis of variance of SIgA measures based on tattoo experience, controlling for age, gender, stress, tattoo session duration, and other covariates mentioned above.

Challenges

Because tattoos often take long periods of time and take place under chaotic circumstances, it is often difficult to collect data on a large number of tattoos in a short time while controlling for various environmental circumstances that can influence study outcomes. We will minimize these difficulties by training student research assistants to observe subjects while they are being tattooed and alert us when it is time to collect saliva samples. This will enable us to collect a high volume of data with maximum integrity. Additionally, we are now working closely with team member Dr. Michael Muehlenbein, who has extensive experience developing means to analyze a wide variety of biological markers of immune response. His collaboration will be critical to achieving a high degree of precision regarding our biological measures.

Pre Analysis Plan

We will test the hypothesis that people with more tattoo experience will have less stress-induced immunosuppression after their tattoo, as measured by immunoglobulin A and cortisol.

Saliva samples will be sent to Baylor University, where Dr. Muehlenbein's team will assay the indicated biomarkers. Questionnaire data will be cleaned by Drs. Lynn and Howells. Based on previous research, we will develop a tattoo experience index by combining Z-scores of years since first tattoo for age, number of tattoos for age, number of hours tattooed for age, and percent of body covered for age. We will regress tattoo experience on post-tattoo measures of immunoglobulin A, controlling for the pretest measure or use repeated measures analysis of variance. Covariates will include cortisol measures, age, BMI, handgrip strength, and current perceived stress.

Variance in our data can be addressed by grouping our participants into high and low tattoo experience groups and deaggregating the factors in the tattoo experience variable to examine individual influences. Furthermore, we that a variety of immunological biomarkers are influenced and that age makes a difference. We will be exploring these other biomarkers and the role of age in immune response.

Finally, tattoo artists have suggested that the types of tools and viscosity of inks involved may be influential, so we will be collected data on these variables and conducting qualitative observations while collecting biological data, as well as making plans for more in-depth future research among those most heavily tattooed.