RESUMO
BACKGROUND: Heritability and population-specific lifestyle factors are considered to significantly contribute to chronic low back pain (LBP), but traditional population studies fail to (1) adjust for genetics; and (2) use standard and validated definitions for LBP and for lifestyle factors. METHODS: Using a classical and a co-twin control study design and validated definitions for chronic LBP and lifestyle variables, we explored the relative contribution of genetics and environment on the prevalence of chronic LBP in a sample of adult Australian twins. RESULTS: Data from 105 twin pairs showed that the prevalence of chronic LBP is significantly determined by genetic factors (heritability = 32%). Additionally, monozygotic twins were five times more likely to have chronic LBP than dizygotic twins when one of the siblings of the pair was affected. In a case-control analysis (n = 38 twin pairs), an exploratory analysis showed higher prevalence of chronic LBP associated with light walking exercises and vigorous gardening or heavy work around the house. Daily time spent in sitting was also positively associated with chronic LBP, but not moderate physical activities such as jogging, cycling and gentle swimming. In the final multivariate model, only time spent in vigorous gardening or heavy work around the house remained associated with chronic LBP (odds ratio 6.5; 95% confidence interval 1.47-28.8). CONCLUSIONS: The type, frequency and duration of physical activity may be important to understand risk factors for chronic LBP. The causation path between chronic LBP and people's engagement in activities involving frequent bending and twisting such as gardening and housework should be further investigated.
