Effects of disclosing hypothetical genetic test results for salt sensitivity on salt restriction behavior

Taro Takeshima,^1,2 Masanobu Okayama,¹ Masanori Harada,³ Ryusuke Ae,⁴ Eiji Kajii<sup>1

1</sup>Division of Community and Family Medicine, Center for Community Medicine, Jichi Medical University, Tochigi, Japan; ²Department of Healthcare Epidemiology, Kyoto University Graduate School of Medicine and Public Health, Kyoto, Japan; ³Department for Support of Rural Medicine, Yamaguchi Grand Medical Center, Yamaguchi, Japan; ⁴Department of General Internal Medicine, Hamasaka Public Hospital, Mikata, Japan

Background: A few studies have explored the effects of disclosure of genetic testing results on chronic disease predisposition. However, these effects remain unclear in cases of hypertension. Reducing salt intake is an important nonpharmacological intervention for hypertension. We investigated the effects of genetic testing for salt sensitivity on salt restriction behavior using hypothetical genetic testing results.
Methods: We conducted a cross-sectional study using a self-completed questionnaire. We enrolled consecutive outpatients who visited primary care clinics and small hospitals between September and December 2009 in Japan. We recorded the patients’ baseline characteristics and data regarding their salt restriction behavior, defined as reducing salt intake before and after disclosure of hypothetical salt sensitivity genetic test results. Behavioral stage was assessed according to the five-stage transtheoretical model. After dividing subjects into salt restriction and no salt restriction groups, we compared their behavioral changes following positive and negative test results and analyzed the association between the respondents’ characteristics and their behavioral changes.
Results: We analyzed 1562 participants with a mean age of 58 years. In the no salt restriction group, which included patients at the precontemplation, contemplation, and preparation stages, 58.7% stated that their behavioral stage progressed after a positive test result, although 29.8% reported progression after a negative result (P < 0.001). Conversely, in the salt restriction group, which included patients at the active and maintenance stages, 9.2% stated that they would quit restricting salt intake following a negative test result, and 2.2% reported they would quit following a positive result (P < 0.001). Age < 65 years (adjusted odds ratio [OR] 1.74; 95% confidence interval [CI] 1.12–2.71), female gender (adjusted OR 1.84; CI 1.29–2.62), graduation from college or university (adjusted OR 1.66; CI 1.11–2.49), and desire for genetic testing (adjusted OR 4.53; CI 3.13–6.57) were associated with progression of behavioral stage in the no salt restriction group. Conversely, salt preference (adjusted OR 2.13; CI 1.31–3.49) was associated with quitting salt restriction in the salt restriction group.
Conclusion: Patients in the no salt restriction group show the possibility of progression from the behavioral stage to the action stage after testing positive for salt sensitivity. Conversely, patients in the salt restriction group, particularly those with a salt preference, would quit salt restriction after testing negative.

Keywords: behavioral change model, salt restriction, hypertension, genetic testing