Factors affecting the prevalence of osteoarthritis in healthy middle-aged women: Data from the longitudinal Melbourne Women's Midlife Health Project
Introduction
Aches and joint symptoms are the most frequently reported symptom in women during midlife [12] and arthritis is the most frequently reported disease [39]. The prevalence of osteoarthritis has been reported to be greater in women than men [16], [29], [43]. The earliest population survey by Lawrence showed radiological evidence of generalized osteoarthritis was three times higher in women aged 45–64 compared to men of the same age group [25]. In addition, a hospital-based study revealed a female to male ratio of 10:1 for osteoarthritis with peak at 50 years of age [45]. Rates of osteoarthritis have been reported as high as 68% in women aged 65 and older [7].
There is evidence that the age period coinciding with the peak age of the menopause is associated with an increased prevalence of osteoarthritis and supports the clinical observation of the increased likelihood of presentation at this age [37]. Sixty-four percent of females with osteoarthritis of knees had the onset of symptoms either perimenopausally or within five years of natural menopause or hysterectomy [32]. Fifty-eight percent of females had onset of symptoms of osteoarthritis of knees before 50 years of age as compared to only 20% in males (P < 0.05) [32]. In a further population-based study of middle-aged women, clustering between joint sites in osteoarthritis was shown to be more common in peri and postmenopausal women than would be expected simply from the rising prevalence of the disorder with age [11].
In addition to this striking difference in prevalence, osteoarthritis is associated with an increased mortality in this group. Epidemiological studies have shown a decreased survival for women with a greater number of joint groups affected with osteoarthritis after adjusting for age (HR 1.45; CI 1.12–1.87 for each increase in 3 joint groups affected with osteoarthritis) [5]. The increased hazard ratio was maintained after adjustment for diabetes, smoking, alcohol use and BMI and also for number of structures affected by osteoarthritis [4].
The effect of increased weight associated with osteoarthritis has been well documented [10], [29], [46] and obesity has been associated with disease progression [17]. Given the variance in the pattern of osteoarthritis in women in addition to the strong influence on weight on the severity of osteoarthritis and the fact that midlife women have an increased tendency for gaining weight [14], [20], the investigation of the relationship between the development of osteoarthritis and weight is particularly important in this population.
Physical activity has been associated with an increased prevalence of osteoarthritis [8], [9], [18], [23], [28], [40], [41], [42], and also with a decreased prevalence of osteoarthritis [30]. The differing results largely reflect the variety of methods used to define physical activity and outcomes assessing osteoarthritis. The balance of evidence seems to suggest that strenuous repetitive activity is traumatic and a risk factor for osteoarthritis whereas modest recreational exercise is a protective factor in its development.
Although age and weight have clearly been associated with increased prevalence of osteoarthritis, the role of physical activity and smoking, in women undergoing hormonal change, have been less well studied. Given women become at risk for osteoarthritis in midlife [34], middle-aged women undergoing menopause are in need of further investigation. In this paper, we examined a cohort of healthy middle-aged women to determine the factors associated with the development of radiological osteoarthritis.
Section snippets
Methods
Participants for this study were obtained from the Melbourne Women's Midlife Health Project, which is a population-based prospective study of Australian born women. The study began in 1991 (baseline) with the use of random digit dialing to interview two thousand and one Australian-born women aged between 45 and 55 years and residing in Melbourne. The response rate was 71%. Seven hundred and seventy-nine of these women were eligible for longitudinal assessment (they had menses in the prior
Results
Questionnaires were completed by 257 participants in the 11th year of follow-up and 224 women underwent X-ray assessment. One hundred and twenty-eight women (56%) had evidence of radiological osteoarthritis involving their hands and/or knees. Forty-nine (21.6%) had evidence of radiological knee osteoarthritis. One hundred and one (44.5%) had evidence of radiological hand osteoarthritis (see Table 1). With respect to radiological assessment of osteoarthritis, there was good agreement of results
Discussion
We observed an influence of physical activity at ages 20–29, BMI and smoking on knee osteoarthritis but not hand osteoarthritis with a beneficial influence of hormone therapy on combined hand and/or knee osteoarthritis. This may be explained by the non-weight bearing nature of the hand joints resulting in different biochemical stresses.
The reason why reported activity ages 20–29 years showed such a significant trend whereas activity at other times did not is an interesting finding. Reporting
Conclusion
Increasing age, BMI and more frequent physical activity in younger years were risk factors for radiological knee osteoarthritis. In contrast, smoking appeared to reduce the prevalence of knee osteoarthritis. Never having used hormone therapy was a risk factor for radiological hand and knee osteoarthritis. Further work will be needed to determine whether modification of these factors can prevent the development of osteoarthritis.
Acknowledgments
X-rays were funded by a grant from the Shepherd Foundation. Dr. Szoeke has received research funding from the Arthritis Foundation of Australia, the University of Melbourne (Viola Edith Scholarship and JA Thompson Prize) and the Royal Australian College of Physicians (Tweedle Fellowship). Data entry and analysis were supported by a grant from the Australian Menopausal Society. The Melbourne Women's Midlife Health Project baseline data collection was funded by the Victorian Health Promotion
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