Men involved in heavy manual labor worry they may end up with a herniated disc. How likely is this occurrence? Who is at risk and why? These are the questions asked by a group of researchers carrying out the Copenhagen Male Study and reported on in this article.
The Copenhagen Male Study was started over 30 years ago. Over 5,000 men participated in the study. They started by completing a survey with questions about the presence of back pain. Many other individual characteristics were also collected (e.g., age, social class, working conditions, height, weight, lifestyle).
By comparing men who reported back pain at the start of the study with men who did not have back pain, they were able to identify risk factors for disc herniation. It's natural to assume that heavy lifting, carrying heavy objects, and sustained postures required by work conditions could contribute to low back problems.
It's also logical that these kinds of problems should decline with age as men perform less strenuous work activities. And there are some experts who suspect height and weight may be predictive risk factors.
The Copenhagen Male Study evaluated a dozen potential risk factors associated with disc herniation in men 40 years old or older. These risk factors included load to the back (low, medium, or high), strenuous work (seldom/never, occasionally, often), and leisure time physical activity (low, medium, high). The effect of other factors such as social class, mental stress (at work, during leisure time), and the use of sedatives, alcohol, or tobacco were also assessed.
One assumption was proven right. The other was not. Physical load and strain were considered risk factors for disc herniation. Reduced risk with age was not the case. Rather, there seems to be a continued (cumulative) effect of heavy lifting, pulling, and pushing.
In other words, over time, the effects of these activities build up and influences disc health even after the man is no longer involved in those activities. Exposure will certainly change for most men over time. After 30 years in this study, many men were past retirement age and no longer engaged in heavy manual labor. Yet, their rate of disc herniation was higher than the younger men who were also involved in heavy physical activity.
When physical activity during leisure time was examined, there was no apparent link to herniated discs. Apparently, the type of physical stress and strenuous physical activity required by leisure activities is not a risk factor for disc degeneration. It’s more likely that the duration of exposure (number of years) is really a very accurate predictor of disc-related back problems later in life.
There was one other key predictive factor of interest and that was physical height. Whereas we once though height and weight measured by the body mass index or BMI was predictive of low back problems, this study highlights the greater influence of height over weight. The taller the person, the greater the risk of disc degeneration.
Knowing that men without a history of back pain but engaged in lifting activities can be at risk for hospitalization for disc herniation is an important finding. With height as a separate, independent risk factor men in jobs requiring manual labor can be identified early. Finding ways to reduce the risk is the next step.
Reference: Inge Gregersen Sørensen, MD, et al. Occupational and Other Predictors of Herniated Lumbar Disc Disease -- A 33-Year Follow-Up in The Copenhagen Male Study. September 1, 2011. Vol. 36. No. 19. Pp. 1541-1546.