Validity of self-reported birthweight among middle-aged and elderly women in the Danish Nurse Cohort Study.

OBJECTIVE: To investigate the validity of self-reported birthweight among middle-aged and elderly women and to identify possible determinants of reporting accuracy. SETTING AND DESIGN: The Danish Nurse Cohort Study (DNCS), a prospective risk factor and hormone therapy study. POPULATION: Participants in the 1999 DNCS. METHODS: Self-reported exact and categorical birthweight data from the DNCS was compared with data from the Copenhagen School Health Records Register (CSHRR), which contains birthweight data. MAIN OUTCOME MEASURES: Accuracy of self-reported birthweight expressed as mean difference with limits of agreement, sensitivity, specificity, and positive and negative predictive values (PPV and NPV). RESULTS: Exact birthweight was available for 441 participants. The correlation coefficient was 0.83. The mean difference was -21 g and limits of agreement were -843 to 818 g. A total of 74% answered correctly within 250 g while 7% were more than 500 g in error. Categorical birthweight was available for 925 participants. A total of 87% reported the correct birthweight. Sensitivity and PPV were high for normal birthweight, whereas specificity and NPV were better for high and low birthweight (HBW and LBW). Multiple logistic regression analyses showed that HBW, LBW and being the daughter of a young mother decreased the accuracy of self-reported birthweight. CONCLUSIONS: Self-reported birthweight is a valid measure of actual birthweight among middle-aged and elderly women. Due to the lower accuracy of HBW and LBW, studies of the association between birthweight and chronic disease may underestimate the true effect of these weights.

Intentional weight loss and mortality among initially healthy men and women.

Most prospective observational studies suggest that weight loss increases the risk of premature death among obese individuals. This is surprising because clinical studies show that weight loss generally leads to overall improvements in cardiovascular risk factors. It is sometimes argued that the increased mortality observed with weight loss must depend on confounding or poor study designs. This review was conducted to summarize results from studies on intentional weight loss and mortality among healthy individuals, while carefully considering the designs and problems in these studies. Evaluation criteria with a rating scale were developed. Of the studies evaluated, two found decreased mortality with intentional weight loss, three found increased mortality, and four found no significant associations between intentional weight loss and total mortality. Thus, it is still not possible for health authorities to make secure recommendations on intentional weight loss. More studies designed to specifically address this issue are warranted.

Influence of health, lifestyle, working conditions, and sociodemography on early retirement among nurses: the Danish Nurse Cohort Study.

AIMS: The aim of the study was to analyze the relationship between health, lifestyle, work-related and sociodemographic factors, and older nurses' exit from the labor market to Post-Employment Wage (PEW). PEW is an early retirement scheme to make it possible for workers to retire at the age of 60. METHODS: The study was based on 5,538 nurses in the age of 51-59 who in 1993 completed a questionnaire on health, lifestyle, working environment, and sociodemographic factors. The survey information was combined with longitudinal data from the Danish Integrated Database for Labor Market Research compiled by Statistics Denmark. The follow-up period was from 1993 to 2002. RESULTS: Nurses who had poor self-rated health were more likely to join PEW compared with nurses who considered their health as good (HR 1.28, 95% CI 1.16-1.41). Low job influence, high workload, and physical job demands only marginally increased the probability of retiring. Nurses who have relatively low gross incomes had an increased probability of entering PEW compared with nurses with relatively high gross incomes (HR 1.60, CI 1.43-1.79). Having a spouse increased the probability of joining PEW, especially having a spouse who had retired or was unemployed. CONCLUSIONS: The retirement age among nurses is influenced by a number of sociodemographic, work-related, and health-related factors. Poor health, low income, living outside the Copenhagen area, being married, having a spouse who is outside the labor force, and working in the daytime are all predictors of early retirement among nurses. Poor working environment only marginally increased the probability of retiring early.

The validity of self-reported fractures among Danish female nurses: comparison with fractures registered in the Danish National Hospital Register.

BACKGROUND: The authors compared self-reported non-spine fractures obtained from a cohort of Danish female nurses with fracture diagnoses registered in the Danish National Hospital Register (DNHR). METHOD: The self-reported fracture history was obtained from a questionnaire and was related to fracture information registered with the DNHR by means of the unique person identification code of Danish citizens. A total of 166 self-reported hip fractures, 391 self-reported wrist fractures, and 121 self-reported upper arm fractures were available for the comparison. The self-reported fractures were initially compared with the anatomic specific fracture diagnoses registered in the DNHR. Second, the comparison also included fracture diagnoses of adjacent skeletal sites (unspecific fracture diagnoses). RESULTS: The positive predictive value of a positive report of hip fracture was 89%. Inclusion of unspecific registered hip fractures increased the positive predictive value to 94%. The same figures for wrist fractures were 75% and 84%, respectively, and for upper arm fractures 54% and 83%, respectively. The predictive value of a negative report of hip fracture was 99.5%. The fracture year was correctly reported in 76% of the hip fracture cases, 81% of the wrist fracture cases, and 82% of the upper arm fracture cases. Predictors of false-positive report of fractures were young age ( < 60 years), report of indoor falls in the previous year, and use of hormone replacement therapy (HRT). CONCLUSION: The authors conclude that self-report of hip, wrist, or upper arm fractures among Danish nurses is relatively accurate but varies by the site of fracture. False positive reports of fracture introduce only modest bias fracture risk estimates and tend to dilute the association between exposures and fracture.

Increased risk of breast cancer following different regimens of hormone replacement therapy frequently used in Europe.

Epidemiologic studies have shown an increased risk of breast cancer following hormone replacement therapy (HRT). The aim of this study was to investigate whether different treatment regimens or the androgenecity of progestins influence the risk of breast cancer differently. The Danish Nurse Cohort was established in 1993, where all female nurses aged 45 years and above received a mailed questionnaire (n = 23,178). A total of 19,898 women returned the questionnaire (86%). The questionnaire included information on HRT types and regimens, reproductive history and lifestyle-related factors. Breast cancer cases were ascertained using nationwide registries. The follow-up ended on 31 December 1999. Women with former cancer diagnoses, women with missing information on HRT, surgical menopause, premenopausal, as well as hysterectomized women were excluded, leaving 10,874 for analyses. Statistical analyses were performed using Cox proportional hazards model. A total of 244 women developed breast cancer during follow-up. After adjustment for confounding factors, an increased risk of breast cancer was found for the current use of estrogen only (RR = 1.96; 95% CI = 1.16-3.35), for the combined use of estrogen and progestin (RR = 2.70; 95% CI = 1.96-3.73) and for current users of tibolone (RR = 4.27; 95% CI = 1.74-10.51) compared to the never use of HRT. In current users of combined HRT with testosterone-like progestins, the continuous combined regimens were associated with a statistically significant higher risk of breast cancer than the cyclical combined regimens (RR = 4.16, 95% CI = 2.56-6.75, and RR = 1.94, 95% CI = 1.26-3.00, respectively). An increased risk of breast cancer was noted with longer durations of use for the continuous combined regimens (p for trend = 0.048). The European traditional HRT regimens were associated with an increased risk of breast cancer. The highest risk was found for the use of continuous combined estrogen and progestin.

Increased risk of stroke in hypertensive women using hormone therapy: analyses based on the Danish Nurse Study.

BACKGROUND: Recent randomized clinical trials suggest an increased risk of stroke with hormone therapy (HT), whereas observational studies have suggested mixed results. Differences in design, definitions of HT exposure, and stroke outcome may explain these discrepancies. Little attention has been paid to identifying subgroups of women who are particularly sensitive to HT. OBJECTIVES: To investigate the risk of various stroke outcomes among women using HT based primarily on estradiol-17beta (unopposed or combined with norethisterone acetate) and to assess the potential modifying effect by presence of risk factors for stroke. DESIGN: Prospective cohort study. SETTING: In 1993, the Danish Nurse Study was established, and questionnaires on lifestyle and HT use were sent to all Danish nurses older than 44 years, of whom 19,898 (85.8%) replied. PARTICIPANTS: Postmenopausal women (n = 13,122) free of previous major cardiovascular and cerebrovascular disease and cancer. MAIN OUTCOME MEASURE: Ischemic or hemorrhagic stroke (n = 144) identified in the national registries of hospital discharges and cause of deaths in the total follow-up through December 31, 1998. RESULTS: In 1993, 28.0% of the 13 122 were current HT users, 14.3% were past users, and 57.7% were never users. Overall, HT exposure was not consistently associated with stroke. However, subdivision based on the presence of hypertension showed a significantly increased risk of stroke among hypertensive women. Compared with hypertensive never HT users, an increased risk of total stroke was found with current use (hazard ratio, 2.35; 95% confidence interval, 1.16-4.74) and especially with current use of estrogen-progestin (hazard ratio, 3.00; 95% confidence interval, 1.33-6.76). Normotensive women had no increased risk of stroke with HT. CONCLUSIONS: We found an increased risk of stroke among hypertensive but not normotensive women using HT. The present study suggests that HT should be avoided in hypertensive women.

Lifestyle factors and choice of hormone replacement therapy among Danish nurses.

BACKGROUND: Studies have found that women who use hormone replacement therapy (HRT) are healthier or report better health than non-users. This study examines the association between lifestyle factors, self-reported health and the use of HRT in Danish female nurses above the age of 50 years. METHODS: Postal questionnaires were used for data collection. Two cohorts were examined, a younger including women between 50 and 59 years and an older including women of 60 years and above. RESULTS: Of the 14,071 nurses included, 5,528 (39%) reported ever using HRT. In both cohorts, ever using HRT was positively associated (odds ratio > 1) with intake of vitamin supplements, alcohol consumption at weekends, consulting a physician, use of medicine, and previous use of oral contraceptives. Only a few differences were found between former and current users of HRT. A highly significant association was found between ever using HRT and self-reported poor health. CONCLUSIONS: In this study use of HRT was not found to be associated with a particularly healthy lifestyle or better health. Therefore, these factors should be specifically considered in studies evaluating the effect of HRT.