Reasons for the increase in chronic LBP are unclear. Changes in the age composition of the state do not explain the increase since the rise in prevalence was similar across all age strata. Ethnic differences also do not explain the increase. As our data indicate, the Hispanic population has a lower prevalence of chronic LBP which is likely due to their younger age. Over 50 percent of the Hispanic individuals surveyed in our study were 21–34 years old. Individuals in this age group, relative to older groups, have a lower prevalence of LBP. An increase in the rate of smoking, a potential risk factor for LBP,(45, 46) is also not a likely explanation for the increase in chronic LBP since rates of smoking in North Carolina adults have decreased slightly over the past decade (26% in 1995, 22% in 2006).(47)