Work and lifestyle factors affecting the risk of disability due to low back disorders tend to be shared among family members, reports a study in the November Journal of Occupational and Environmental Medicine, official publication of the American College of Occupational and Environmental Medicine (ACOEM).

The report was part of a continuing study of risk factors for future disability pension from low back disorders, based on a large sample of Finnish twins. The use of twin data helps to evaluate possible familial factors affecting risk. The lead author was Annina Ropponen, PhD, of the University of Eastern Finland, Kuopio.

Several work-related factors were linked to an increased risk of disability pension: monotonous work, lifting and carrying, physically heavy work, and previous unemployment. A healthy lifestyle predicted a lower risk of back-related disability.

However, when disability risk was compared between twin pairs, nearly all of the risk factors were "due to family background or other factors shared by co-twins," the researchers write. In other words, the work-related and lifestyle factors that increased the risk of disability pension for back disorders were largely explained by familial factors -- whether related to genetics, social background, or both.

"The effect of familial confounding highlights the importance of some early childhood factors or habits shared among family members," according to Dr Ropponen and colleagues. For example, factors like exercise, smoking or body weight are influenced by family background, which in turn affects disability risk.

"This may suggest that adopting a healthy lifestyle early in life is important if one wishes to avoid disability pension," the authors add. They note that their study is limited by the relatively small number of "discordant" twins -- that is, one twin on disability and the other off disability.