(RxWiki News) Osteoarthritis, known as “wear and tear” arthritis, affects more than 20 million people in the US. Avoiding undue stress on your joints early on makes a huge difference in old age.
Being overweight can put added stress on the joints and is associated with a higher risk of osteoarthritis. Weight loss through exercise can prevent the progression of the disease. But on the other hand, exercise may put undue stress on joints.
It might be better to introduce lifestyle changes early in life, according to results from the Melbourne Collaborative Cohort Study.
The study showed that both weight gain and being overweight from early to middle adulthood were associated with the risk of joint replacement surgery in later life.
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The study was conducted by Yuanyuan Wang, PhD, from the School of Public Health and Preventive Medicine at Monash University's Alfred Hospital in Melbourne, Victoria, and colleagues from other academic institutions in Australia.
The aim of this study was to find out if there was a relationship between body weight and the risk of needing total knee and hip replacement for osteoarthritis.
The authors conducted the study with 41,514 participants aged between 27 and 75 years, with mean age of 54.9 years. The study began in 1990 and participants were followed over several years to evaluate the effects of weight and weight gain.
Height and weight were measured at the start of the study to calculate body mass index (BMI), a ratio of weight to height. These measures were classified as weight and BMI at middle age. Participants were asked also to recall their weight when they were 18 to 21 years of age, and this measure was classified as weight at early adulthood.
Normal weight was defined as BMI less than 25 kg/m2 and overweight as any BMI higher than 25 kg/m2.
Most of the participants (52 percent) were normal weight during early adulthood and became overweight in middle age. Very few participants (12 percent) were overweight at both ages and even fewer (1 percent) were overweight in early adulthood and normal weight at middle age.
The researchers conducted face-to-face interviews with the participants about their first joint replacement surgery. The participants were asked if they had ever had a hip or knee replacement and when. Their answers were confirmed using the Australian Orthopaedic Association’s National Joint Replacement registry records between 2001 and 2009.
Over about eight years of follow-up, the overweight population had significantly more joint replacement procedures performed than the individuals who were normal weight and had not gained weight in early adulthood or middle age.
The researchers also calculated hazard ratios for the three factors affecting the risk of replacement surgery: middle-age weight, BMI and weight gain.
A hazard ratio in this case was used to compare two groups both with negative outcomes. So a higher hazard ratio indicated that the particular group had a higher risk of developing the negative outcome over the other group.
The hazard ratio for knee replacement according to middle-age body weight was 1.25 for each 5 kg of weight above normal, compared to a hazard ratio of 1 for hip replacement.
The hazard ratio for knee replacement according to BMI was 1.80 per 5 kg/m2 over normal BMI, compared to a hazard ratio of 1.29 for hip replacement. The hazard ratio for adult weight gain was 1.25 per 5 kg weight gain for knee vs 1.10 for hip.
These findings suggest that weight-related factors are bigger risks for knee replacements than hip replacements. The authors attributed this difference to the differences in weight bearing abilities of knee versus hip joints.
The association between BMI at middle age and total hip replacement risk was greater for men than for women. According to the authors, this difference may be due to hormonal factors, anatomical hip structure and different types of occupations chosen by the two genders.
One limitation of the study may appear to be the self-reporting of past weight that relied on participants’ memories. But the authors cited other studies to show that such measures have been reliable in past epidemiological studies.
Overall, the study found that higher weight and BMI at early adulthood and middle age, weight gain during this time and persistent overweight during the entire study were all associated with a higher risk of total knee and hip replacement. The association was higher for knee replacements than hip replacements.
“Weight control from early adulthood and avoiding weight gain are important for the prevention of osteoarthritis,” the authors concluded.
The results of the study were published in the June issue of Rheumatology.
The study was funded by grants from the National Health and Medical Research Council and supported by infrastructure provided by Cancer Council Victoria. No conflicts of interest were declared.
