Clearwater Study Results Presented - Winter 1993

Although the Arthritis Research Institute of America's Clearwater Study is an ongoing, 25-year investigation of all possible aspects of osteoarthritis, preliminary results of specific-studies, within the overall investigation continue to be made public.

Recently two of the Institute's scientific abstracts, both related to osteoarthritis in the knee, were presented at the American College of Rheumatology.

One of the two abstracts focused on Factors Associated with Knee Osteoarthritis and the other specifically addressed the relationship between Physical Activity and Knee Osteoarthritis. The highlights of those abstracts follow:

Factors Associated with Knee Osteoarthritis

In this study, ARIA researchers evaluated possible risk factors for knee osteoarthritis in a group of 581 male and 1,223 female participants in the Clearwater Study.

Among the risk factors considered were smoking, blood pressure, diabetes, total body weight, current and past body mass index, and body fat distribution, as well as certain demographic characteristics.

The study found that current body mass index, total body weight, and body mass index at age 25 and 45 are age-independent predictors of knee osteoarthritis for both males and females. The researchers also concluded that obesity, as measured by body mass index, increases the risk of knee osteoarthritis in a "dose" dependent manner. In other words, the greater the obesity, the greater the risk of knee osteoarthritis.

In addition to obesity, however, the researchers also focused closely on the possible role of total body weight in the development of knee osteoarthritis and also found a strong association between the two, regardless of age.

Lastly, the study used the waist/ hip ratio to investigate the relationship of body fat distribution and knee osteoarthritis among females. The researchers reported that "although our findings are not supportive of an independent role for central body fat as a risk factor for knee osteoarthritis, we consider the issue should be further studied.

Physical Activity and Knee Osteoarthritis

This study, intended to add to a limited body of research into physical activity as a possible risk factor for knee osteoarthritis, involved a total of 512 participants, 332 males and 180 females.

Half the participants (cases) had radiologically confirmed diagnosis of knee osteoarthritis, while the other half (controls) were free of symptoms and showed no radiologic evidence of knee osteoarthritis.

Study participants, in addition to receiving a physical examination, were asked about their adult lifetime work history, their leisure sport activities (including home-based ones) and whether they exercised continuously for at least 20 minutes three times a week (with the specific kind of exercise defined). The level of physical activity among participants was divided into two categories, high (participation in very hard, hard, and moderate activities) and low (participation in low, or no, activities).

The findings showed that highly active females, particularly those aged 55-64 are at increased risk of developing knee osteoarthritis. The study also demonstrated gender differences to high levels of "cumulative" physical activity as a risk factor in development of the disease.

When occupational, leisure sports participation and home based activities are combined as a cumulative exposure, females aged 55-64 are at increased risk of the disease and males are apparently not. The researchers involved in the study recommend that the reasons for this apparent risk by gender be investigated further, suggesting that hormonal changes which accompany aging in women may be, at least in part, responsible while there may also be inherent unidentified protective factors in the male population.

The researchers also warn that more study needs to be done, especially in the area of exercise as a risk factor versus the long-term benefits of supervised exercise programs for individuals with knee osteoarthritis.

ARIA's Clearwater Study is a long-term, large scale population study which compares in scope to the world famous Framingham Heart Study. That investigation began back in 1950 by monitoring 5,290 residents of Framingham, Massachusetts, and still continues today.

Some 5,000 people have been enrolled in the Clearwater Study, which began in 1985 and will continue for a 25-year period. In the study, the Institute is focusing in particular on such factors as heredity, obesity, occupation, injury and personal lifestyle, both in the onset of the disease and the degree to which it progresses.

Progress Continues in Clearwater Study - Winter 1997

1997 will mark the 12th year of the Clearwater Study as it nears the halfway point of its planned 25-year span.

This closely-watched effort involves intensive study of 5,000 Americans throughout as much of the life of the study as possible.

Easily the most extensive investigation of osteoarthritis ever conducted, the Clearwater Study will ultimately provide an understanding of the involvement, or non-involvement, of such factors as heredity, obesity, occupation, injury and personal lifestyle, both in the onset of the disease and the degree to which it progresses.

In that sense, it is hoped, and expected, that the Clearwater Study will have the same impact on osteoarthritis as the famed Framingham Study has had on heart disease. The parallels between those two studies are great and involve much more than the large numbers of individuals involved and the long-term conduct of the research itself.

For example, osteoarthritis today is still considered by many, if not most, Americans to be simply part of the aging process, something that happens to us as we grow older.

What many people don't remember is that the same thing was held true about heart disease until very recently. The Framingham Study helped the medical community - and the American people - see that heart disease, rather than an inevitable consequence of growing old, is tied to a number of risk factors such as smoking, cholesterol levels, obesity and others.

And indeed, even at this stage of its conduct, the Clearwater Study has already led to related investigations that study some of those same factors for their possible involvement in the onset of osteoarthritis or in the degree to which it inflicts pain and immobility on its victims.

Those related investigations are exploring the roles of obesity and other such possible risk factors as smoking, blood pressure, diabetes, total body weight, current and past body mass indices, body fat distribution, even demographic characteristics.

Furthermore, the Framingham Study helped pave the way for not only a significant awakening to the role of exercise in the development or avoidance of heart disease, but also for massive nationwide education into the benefits to be derived from proper exercise and encouragement of all Americans to engage in such heart-healthy activities.

Similarly, in a program that has already attracted a great deal of attention from the medical and scientific community, the Clearwater Study has also launched a thorough exploration of the role of exercise as a contributor to, or a preventor of, osteoarthritis. Another exercise study seeks to compare the possible benefits to osteoarthritis patients of a carefully planned and monitored weightlifting program with certain aerobic exercise.

Of course, all findings from the Clearwater Study and the other investigations are added on a regular basis to the growing database of computer information gathered from the studies. This information is constantly requested by, and provided to, epidemiologists and other concerned physicians, scientists and researchers all across the country