Risk factors for hip fracture and a possible effect modification by hormone replacement therapy. The Danish nurse cohort study.

OBJECTIVE: To identify risk factors for hip fracture and to examine whether hormone replacement therapy (HRT) modifies the effect of these risk factors. DESIGN: Prospective cohort study. SETTING: The Danish Nurse Cohort Study. PARTICIPANTS: 14,015 female nurses aged 50 years and above who in 1993 completed a questionnaire on general health and lifestyle issues, reproductive history including information on HRT, and family history of osteoporosis and personal history of a wrist fracture. OUTCOME MEASURES: End-point was the first-ever hip fracture registered in the Danish National Hospital Register during the period from 1993 to 1999. RESULTS: During the follow-up period 245 hip fractures were identified. Ever users of HRT had a lower risk of hip fracture (hazard ratio 0.69; 0.50-0.94). Women reporting a poor health (hazard ratio 2.01; 1.30-3.11), restrictions in daily activities (hazard ratio 1.52; 1.05-2.21), low body mass index (hazard ratio 1.65; 0.98-2.77), and leisure time sedentary physical activity (hazard ratio 1.88; 1.30-2.70) were main identified risk factors for hip fracture. HRT did not modify the effect of risk factors on the risk of hip fracture. CONCLUSION: This study confirms that women with a frail health are at increased hip fracture risk and that ever use of HRT decreases the risk of hip fracture. HRT did not modify the effect of these risk factors, indicating that the preventive effect of this therapy is independent of risk factors.

The validity of self-reported use of hormone replacement therapy among Danish nurses.

BACKGROUND: Recent findings from randomized clinical trials on the effects of hormone replacement therapy (HRT) among postmenopausal women contradict findings from observational studies indicating a protective effect on the development of cardiovascular disease. Most observational studies on HRT are based on self-reported data, although data on the validity of HRT in postmenopausal women are sparse. METHODS: We examined self-reported HRT use from questionnaires administered in 1993 (n = 2694) and again in 1999 (n = 2666) to a cohort of Danish nurses living in two Danish counties compared with prescription-reimbursement data from two administrative databases through the Danish National Health Service. RESULTS: The sensitivity and specificity of the self-reported, current HRT use in 1993 were 78.4%[95% confidence interval (95% CI) 75.4-81.4] and 98.4% (95% CI 97.8-98.9), respectively. In 1999, the estimates were 74.8% (95% CI 72.0-77.7) and 98.0% (95% CI 97.3-98.8), respectively. None of the factors examined--including age, alcohol intake, physical activity, smoking, presence of hypertension, and body mass index--was strongly associated with validity. We found a relatively high validity of self-reported data on HRT use. Furthermore, agreement between self-reported and registry-based data was not strongly associated with a range of demographic and lifestyle factors. CONCLUSION: These findings suggest that use of self-reported data is not an important contributor to the apparent discrepancy between observational studies and randomized trials on the cardiovascular effects of HRT use.

Risk of low-energy hip, wrist, and upper arm fractures among current and previous users of hormone replacement therapy: The Danish Nurse Cohort Study.

OBJECTIVE: To examine the effect of oestrogen alone and in combination with progestin on the risk of low-energy, hip, wrist, and upper arm fractures. Additionally, to examine to what extent previous use, duration of use as well as recency of discontinuation of hormone replacement therapy (HRT) influences the fracture risk. DESIGN: Prospective cohort study. SETTING: The Danish Nurse Cohort Study PARTICIPANTS: 7082 female nurses aged 50-69, who completed a questionnaire on lifestyle and use of HRT in 1993. OUTCOME MEASURES: Self-reported low-energy, hip, wrist, and upper arm fractures between 1993--1999 obtained at a re-examination in 1999. RESULTS: Compared to never users, current users of HRT, either oestrogen alone or combined with progestin, had a lower risk of low-energy, hip, wrist, and upper arm fractures (hazard ratio 0.60, 0.39-0.93 and hazard ratio 0.44, 0.30-0.66, respectively). The protective effect of HRT appeared to be significantly restricted to users who used the therapy for 10 years or more (hazard ratio 0.27, 0.14-0.51). Women who previously used hormones experienced no protective effect on fracture risk regardless of duration of therapy and recency of discontinuation. CONCLUSION: Only long-term HRT (10 years or more) offers a protective effect against low energy, hip, wrist, and upper arm fractures. In women with risk factors or established osteoporosis, benefits and risks of this therapy should be balanced when considering its use as a first line treatment for prevention of these fractures.

Use of hormone replacement therapy among Danish nurses at increased risk of osteoporosis.

Observational studies and recent randomized trials have shown that postmenopausal hormone replacement therapy (HRT) may reduce the risk of osteoporotic fractures by about 30 to 40%. In this study we used a log linear graphical model to determine whether women with a known increased risk of osteoporosis were more likely to use HRT than other women and to examine whether women at increased risk modified this risk through their lifestyle. Cox regression analysis was used to analyze if women at risk of osteoporosis used HRT longer than women not at risk. Participants were Danish female nurses who, in 1993, were between 50 and 69 years of age (N=14,865). Data were collected from postal questionnaires. We concluded that nurses with a known family history of osteoporosis more often used HRT than nurses without this risk. No other direct associations were found between biological risk factors and ever use of HRT. The presence of biological risk factors of osteoporosis was not consistently modified by a healthier lifestyle. Nurses with a low body mass index (BMI) with a known family history of osteoporosis continued to use HRT longer than nurses without these risk factors.