Body mass as a determinant of seat belt use

Prevention of death and injury from motor vehicle accidents depends in part on seat belt use. Understanding the determinants of seat belt use is important for developing strategies to increase seat belt use. The cross-sectional association between body mass index (BMI) and self-reported seat belt use was analyzed using data from 3,140 Health Risk Appraisals completed by Tennessee residents during 1986. Persons in the lowest quintile BMI (≤21.8 kg/m²) stated they use seat belts 63% (SD=38%) of the time compared to persons in the highest BMI quintile (≥29.0 kg/m²) who reported using seat belts 50% (SD=38%) of the time. BMI remained associated with seat belt use after adjustment for age, sex, race, education, cigarette use, alcohol use, drug use, urban/rural residence, state area of residence, miles driven per year, self-reported physical activity, and satisfaction with life. For a 1 kg/m² increase in BMI, seat belt use declined -0.73% (95% CI=-1.01, -0.46), and the relative odds of not being a frequent seat belt user increased 3% (odds ratio 1.03, 95% CI=1.01, 1.05). BMI was the third variable selected in a step-wise multiple linear regression after education and race. The BMI/seat belt association, if causal, has implications for (1) targeting of education programs to likely nonusers by traffic safety agencies; (2) targeting health promotion messages to likely nonusers by primary care providers; and (3) design of automobile seats and restraint devices.