Associations of general and abdominal obesity with multiple health outcomes in older women: the Iowa Women's Health Study.

BACKGROUND: Recent clinical guidelines on the health risks of obesity use body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters) and waist circumference, but the waist-hip ratio may provide independent information. METHODS: To assess the joint and relative associations of BMI, waist circumference, and waist-hip ratio with multiple disease end points, we conducted a prospective cohort study of 31,702 Iowa women, aged 55 to 69 years and free of cancer, heart disease, and diabetes, assembled by random sampling and mail survey in 1986. Study end points were total and cause-specific mortality and incidence of site-specific cancers and self-reported diabetes, hypertension, and hip fracture over 11 to 12 years. RESULTS: The waist-hip ratio was the best anthropometric predictor of total mortality, with the multivariable-adjusted relative risk for quintile 5 vs 1 of 1.2 (95% confidence interval, 1.1-1.4), compared with 0.91 (95% confidence interval, 0.8-1.0) for BMI and 1.1 (95% confidence interval, 1.0-1. 3) for waist circumference. The waist-hip ratio was also associated positively with mortality from coronary heart disease, other cardiovascular diseases, cancer, and other causes. The waist-hip ratio was associated less consistently than BMI or waist circumference with cancer incidence. All anthropometric indexes were associated with incidence of diabetes and hypertension. For example, women simultaneously in the highest quintiles of BMI and waist-hip ratio had a relative risk of diabetes of 29 (95% confidence interval, 18-46) vs. women in the lowest combined quintiles. CONCLUSION: The waist-hip ratio offers additional prognostic information beyond BMI and waist circumference.

Assessing change in diet-intervention research.

In nutrition-intervention research, it is important to consider the sensitivity of dietary assessment instruments to the changes in nutrient intake or dietary behavior under study. This presentation describes a measure called "responsiveness," an index of an instrument's sensitivity to change. Illustrations of this measure are from two randomized dietary-intervention trials that targeted reductions in fat intake: the Women's Health Trial (WHT), a trial to test whether fat reduction would reduce the risk of breast cancer, and the Eating Patterns Study (EPS), a trial to evaluate a self-help booklet to promote dietary change. In the WHT, a 4-d diet record (FDDR) was only slightly more responsive to dietary change than was a food-frequency questionnaire (FFQ). In the EPS, a fat-related diet-habits questionnaire was most responsive, followed by an FDDR and an FFQ. These data suggest that short, inexpensive measures such as FFQs or questionnaires that assess dietary habits can be as responsive as multiple-day diet records. More research is needed on the relative responsiveness of dietary assessment tools. Intervention studies should include at least two types of dietary assessment tools and the relative validity, reliability, and responsiveness of these tools should be reported as part of the study outcome.

Diabetes and endometrial cancer in the Iowa women's health study.

Diabetes has been associated with increased risk of endometrial cancer in some epidemiological studies. Body mass index (BMI) and other measures of obesity have been associated positively with both diabetes and endometrial cancer. It is not clear whether or not the association of diabetes with endometrial cancer is explained entirely by obesity. Thus, we sought to test the hypothesis that diabetes is not associated with endometrial cancer independent of obesity. We examined the association between self-reported diabetes (onset at >30 years of age) and incident endometrial cancer in a prospective cohort study of 24,664 postmenopausal women in Iowa. Over 12 years of follow-up, 346 cases occurred among the cohort at risk. Data were analyzed using proportional hazards regression models. Diabetes was analyzed as reported at baseline and as a time-dependent variable using information obtained during follow-up. After adjustment for BMI, waist:hip ratio, and other covariates, the relative risk (RR) for women with diabetes versus women without diabetes was 1.43 [95% confidence interval (CI), 0.98-2.1]. The diabetes association was confined to women in the upper two BMI quintiles (RR, 1.47; 95% CI, 0.98-2.20), but a formal test of interaction was not statistically significant. Analyses that included diabetes ascertained at baseline and at follow-up gave similar results; the diabetes-associated RR in the higher BMI strata was 1.64 (95% CI, 1.16-2.31). We conclude that after adjustment for other risk factors, diabetes is associated with a modestly increased risk for endometrial cancer among women in this cohort.

Change in the use of breast-conserving surgery in western Washington after the 1990 NIH Consensus Development Conference.

OBJECTIVE: To evaluate the use of breast-conserving surgery in western Washington before and after the National Institutes of Health Consensus Development Conference (June 18-21, 1990) during which breast-conserving surgery was recommended for most women with early invasive breast cancer. DESIGN: Survey. SETTING: Population-based cancer registry in the Seattle-Puget Sound (Washington) region. PARTICIPANTS: The survey included 13541 women in whom American Joint Committee on Cancer stage I or II breast cancer was diagnosed between January 1, 1983, and December 31, 1993. MAIN OUTCOME MEASURE: Proportion of participants who underwent breast-conserving surgery. RESULTS: From April 1985, after results of a US randomized controlled trial showing equivalent survival in women undergoing mastectomy or breast-conserving surgery were published, to the time of the Conference, breast-conserving surgery was performed on 44.8% of women with stage I and 25.8% with stage II breast cancer. These percentages increased to 54.9% and 35.2%, respectively, during the post-Conference period. While women with stage II breast cancer were less likely than women with stage I breast cancer to undergo breast-conserving surgery before and after the Conference, trends for age and education were attenuated after the Conference. Differences in the use of breast-conserving surgery observed before the Conference between countries of residence and among hospital types were also reduced after the Conference. CONCLUSIONS: These findings suggest that the Conference recommendations had an effect on the adoption of breast-conserving surgery, particularly among groups who were previously least likely to undergo such surgery. Despite progress toward the Conference recommendation that the majority of women with early invasive breast cancer undergo breast-conserving surgery, the majority of women with stage II breast cancer undergo mastectomy.

A case-control study to evaluate efficacy of screening for faecal occult blood.

OBJECTIVES: Faecal occult blood testing is routinely used for early detection of colorectal cancer, but evidence of its efficacy in preventing death from colorectal cancer is limited. A case-control study was carried out to evaluate whether screening for faecal occult blood is associated with a reduced risk of fatal colorectal cancer. SETTING: A health maintenance organisation in western Washington State, which has offered its members faecal occult blood testing every two years since 1983. METHODS: Cases (n = 248) were members of the health maintenance organisation who died from colorectal cancer between 1986 and 1991. For each case, two control subjects, who did not die from colorectal cancer and who were similar to each case in age, gender, and year of enrollment at the health maintenance organisation, were randomly selected from the membership list of the year in which the case was diagnosed (n = 496). Information about episodes of faecal occult blood testing (including the location and reason for the test, and the evaluation of positive tests) and potential confounders was obtained from medical records. RESULTS: Cases were less likely than controls to have ever been screened (odds ratio (OR) = 0.7, 95% confidence interval (CI) 0.5 to 1.0), consistent with a beneficial impact of screening. There was little difference, however, for screening that had taken place within a three year period before diagnosis (OR = 0.9, 95% CI 0.6 to 1.2), the maximum interval during which most tumours ought to have been detectable by faecal occult blood testing. A reduction in risk was seen for home testing but not for office testing, and in individuals aged less than 75 but not in those aged 75 or older. Although most of the 21 controls with a positive faecal occult blood test underwent some additional testing, only five (24%) were evaluated with colonoscopy or air contrast barium enema. CONCLUSIONS: While there can be uncertainty as to whether specific faecal occult blood tests were performed as screening or diagnostic tests, those performed at home and in younger persons may be relatively less likely to be diagnostic tests that were misclassified as screening. Thus the modest reduced risk associated with faecal occult blood testing in these settings/persons may reflect genuine benefit. However, the presence of a reduced risk associated with a screening faecal occult blood test received in the past, well before a tumour or polyp might bleed enough to allow detection, is compatible with uncontrolled confounding. Interpretation is further complicated by the fact that a number of individuals in the study group who had positive test results underwent limited or no diagnostic testing. Thus our results should be interpreted with considerable caution.

Knowledge and preference for breast conservation therapy among women without breast cancer.

We interviewed 419 adult women in Minnesota, who were selected at random and without a history of breast cancer, to ascertain what percentage could correctly report that cure was the same for breast conservation therapy and mastectomy, what percentage would state a preference for breast conservation therapy rather than mastectomy, and characteristics associated with these outcomes. Nearly all women (n = 360; 86%) had heard of both mastectomy and breast conservation therapy; among these women, 37% correctly reported that the two treatments were equally efficacious. Given a scenario where they were diagnosed with breast cancer amenable to either treatment, 58% of participants stated a preference for breast conservation therapy. Older women were less likely than younger women to know that cure was the same for breast conservation therapy and mastectomy (adjusted OR = 0.5, 95% CI 0.2, 1.0), and women residing in urban areas were more likely to prefer breast conservation therapy over mastectomy compared to rural residents (adjusted OR = 2.2, 95% CI 1. 3, 3.8). Comparing these findings to women diagnosed with breast cancer in Minnesota, breast conservation therapy was found to be performed less frequently than preference for such therapy among women in our study would suggest. Educating women prior to diagnosis about breast cancer treatment options, and exploring reasons for the gap between actual utilization of breast conservation therapy and prediagnosis preference, may be indicated.

Implementing a dietary intervention in primary care practice: a process evaluation.

OBJECTIVES: Physicians acknowledge the need to advise their patients about dietary habits, but they may not have the training or tools to do this efficiently. In the context of a randomized trial, we investigated the feasibility of enlisting physicians to implement a dietary intervention in the primary care setting. METHODS: Physicians from 14 primary care practices were assigned via randomization to introduce a self-help booklet to promote dietary change at routine appointments. Delivery of the booklet was recorded by these intervention physicians at the clinic appointment; intervention participants were asked 3 months later in a telephone interview about whether they received and used the booklet. RESULTS: According to physician documentation, 95% of intervention participants who kept an appointment (n = 935) received the booklet; among participants completing a 3-month interview (n = 890), 96% reported the same. However, only about 50% of participants reported receiving the booklet from their physician; the remainder received the booklet from other clinic staff. Overall, 93% reported reading at least part of the booklet. Use of the booklet varied little whether it was delivered by a physician or staff person, but it was more likely to be read as time spent discussing the booklet increased. CONCLUSIONS: Physician cooperation and evidence of intervention effectiveness support the use of primary care for the delivery of interventions to change diet; training the entire health team and repeating dietary advice at subsequent visits may improve the success of such interventions.

Effect of health lifestyle pattern on dietary change.

PURPOSE: To examine the effect of lifestyle on the effectiveness of a low-intensity dietary intervention. DESIGN: A secondary data analysis was performed using data from the Eating Patterns Study, a randomized controlled trial that found that self-help materials with physician advice was effective in changing dietary intake and behavior. SETTING: Primary care clinics in a large health maintenance organization. SUBJECTS: A total of 2111 patients with a routine scheduled appointment with their primary care physicians. MEASURES: Participants were grouped into one of six health lifestyle patterns based on similarities in baseline measures of alcohol intake, smoking, diet quality, and exercise. Within each lifestyle pattern, changes from baseline in usual fat and fiber intake (based on a food frequency) and a fat and fiber behavior score were compared at 3 months and 12 months for intervention vs. control participants. INTERVENTION: Self-help materials delivered by a physician with advice to change diet. RESULTS: Intervention participants in the fitness lifestyle group made the largest changes relative to controls for each dietary outcome at 3 and 12 months. For intervention participants defined by their alcohol intake or current smoking, either no changes in diet were observed compared with controls, or early changes were not sustained over time. Intervention-control comparisons within the remaining lifestyle patterns showed smaller dietary changes compared with the fitness lifestyle. This finding was similar to previously published results. CONCLUSIONS: This randomized controlled trial had limited power to detect subgroup differences; however, these results suggest that lifestyle patterns may be useful in the development of effective, targeted interventions to change behavior.

Impact of the Mammography Quality Standards Act on access in Minnesota.

OBJECTIVES: The Minnesota Department of Health surveyed registered mammography facilities to assess their accreditation status prior to full implementation of the Federal Mammography Quality Standards Act (MQSA), which mandated accreditation of all mammography facilities by October 1994; to strategize on the steps that might be taken to avoid closure of facilities; and to evaluate the ultimate impact of the law on the availability of mammography in Minnesota. METHODS: Mammography facilities registered with the Radiation Control Section of the state health department were surveyed five months prior to and four months after the October 1994 deadline. Data collected included accreditation status, plans for continuing service, number of mammograms performed, and areas in which technical assistance was needed. In October 1995, the number and distribution of facilities were determined from the Radiation Control Section registration database. RESULTS: The pre-MQSA survey of 182 respondents found that 96% planned to continue mammography services but only 49% were accredited. The remaining 51% had applications in progress. In the post-MQSA survey, 70% of 182 facilities were found to be accredited, and 30% were operating under provisional certification. As of October 1995, although six facilities had closed, there was a net gain of four mammography facilities providing on-site service. CONCLUSIONS: Despite fears to the contrary, access to mammography in the state of Minnesota was not adversely affected by full implementation of the Mammography Quality Standards Act.

Vitamin D status among long-term survivors of hematopoietic cell transplantation.

Little is known about serum vitamin D levels following hematopoietic cell transplantation (HCT). Patients are instructed to avoid sun exposure because of an increased risk of skin cancers. Altered gastrointestinal absorptive capacity as a result of GVHD, bile acid or pancreatic enzyme insufficiency or bacterial overgrowth may lead to difficulty in absorbing the fat-soluble vitamin D. This study was undertaken to determine the prevalence of serum 25-hydroxyvitamin D (25(OH)D) deficiency, and factors associated with 25(OH)D deficiency, among children and adults who were at least 1 year following HCT. A total of 95 participants (54 males and 41 females) completed a questionnaire on usual diet and lifestyle, and provided a blood sample for 25(OH)D determinations between November 2008 and July 2009. The majority of participants had serum 25(OH)D levels ≥75 nmol/L (n=62, 65%), 23 had insufficient levels (50-75 nmol/L) and 10 participants were deficient (<50 nmol/L). The majority of participants reported regular use of vitamin D supplements (n=58, 61%). Prednisone use was significantly inversely associated with serum 25(OH)D concentrations. Total vitamin D intake was the strongest single predictor of 25(OH)D concentrations. These findings suggest that 400-600 IU vitamin D per day appears to be required to achieve optimal serum 25(OH)D concentrations following HCT.

Breast carcinoma after cancer at another site: method of detection, tumor characteristics, and surgical treatment.

BACKGROUND: As the number of cancer survivors increases, so will the number of second primary cancers, including breast carcinoma after cancer at another site. Limited information is available regarding the clinical characteristics of breast carcinoma after a primary at another site. METHODS: TUMORS (The Upper Midwest Oncology Registry Services) was used to identify 937 women with breast carcinoma occurring as a second primary after a first primary at a known site other than the breast. They were compared with a sample of 1874 women with first primary breast carcinoma, frequency-matched by age to the second primary group, for method of detection, tumor characteristics, and type of surgery. RESULTS: Women with breast carcinoma after cancer at another site tended to have smaller tumors and less extensive disease than women with first primary breast carcinoma and were somewhat more likely than first primary cases to have had their breast carcinoma detected by mammogram or clinical breast exam rather than detecting it themselves. Differences in method of detection accounted for differences in tumor size and extent. Second primary breast carcinoma was less likely to be lobular or mixed ductolobular carcinoma compared with first primary breast carcinoma. Surgical treatment (mastectomy vs. breast-conserving surgery) did not differ for first and second primary breast carcinoma. CONCLUSIONS: Clinical characteristics of breast carcinoma after cancer at another site were by and large similar to those of first primary breast carcinoma. The more favorable prognostic characteristics among women with a history of cancer were accounted for by increased medical surveillance.

Underutilization of breast-conserving surgery and radiation therapy among women with stage I or II breast cancer.

OBJECTIVE: To identify time trends and factors associated with breast-conserving surgery (BCS) and delivery of postoperative radiation therapy among women with stage I or II breast cancer. DESIGN: Survey. SETTING: Population-based cancer registry in the Seattle-Puget Sound (Wash) region. PARTICIPANTS: The study included 8095 women diagnosed with stage I or II breast cancer (American Joint Committee on Cancer staging criteria) from 1983 through 1989. MAIN OUTCOME MEASURES: Breast-conserving surgery with or without radiation therapy vs mastectomy, and, among women with BCS, a comparison of radiation therapy vs no therapy. RESULTS: In 1985 when results from a US randomized clinical trial of BCS were published, the frequency of BCS peaked (46.3% of stage I; 30.1% of stage II) followed by a return to levels before 1985 for women with stage II breast cancer and a more moderate decline for stage I breast cancer. The likelihood of BCS decreased with increasing age (P less than .001), with stage II disease, and with residence outside the region's major urban center, and it increased with education (P less than .001) or median income (P less than .001) by census tract. The proportion of women who received radiation therapy after BCS decreased with age (P less than .001), was lower for women with stage II than stage I disease, and was lowest in counties without radiation therapy facilities. CONCLUSIONS: Despite scientific evidence of the equivalent efficacy of BCS with radiation therapy and mastectomy, BCS is not performed on the majority of women with stage I or II breast cancer as recommended by the National Institutes of Health, and factors are associated with its use that differ from selection criteria outlined by the National Institutes of Health.

Vitamin A intake and the risk of hip fracture in postmenopausal women: the Iowa Women's Health Study.

Excessive intake of vitamin A is postulated to have a detrimental effect on bone by inducing osteoporosis. This may lead to an increased risk of fracture, particularly in persons who are already at risk of osteoporosis. However, few studies have specifically examined the association of vitamin A intake through diet and supplement use, with fractures in a cohort of older, community-dwelling women. We prospectively followed a cohort of 34,703 postmenopausal women from the Iowa Women's Health Study to determine if high levels of vitamin A and retinol intake through food and supplement use were associated with an increased risk of hip or all fractures. A semiquantitative food frequency questionnaire was used to obtain the participants' baseline vitamin A and retinol intake. Participants were followed for a mean duration of 9.5 years for incident self-reported hip and nonhip fractures. After multivariate adjustment, it was revealed that users of supplements containing vitamin A had a 1.18-fold increased risk of incident hip fracture (n = 525) compared with nonusers (95% CI, 0.99 to 1.41), but there was no evidence of an increased risk of all fractures (n = 6,502) among supplement users. There was also no evidence of a dose-response relationship in hip fracture risk with increasing amounts of vitamin A or retinol from supplements. Furthermore, our results showed no association between vitamin A or retinol intake from food and supplements, or food only, and the risk of hip or all fractures. In conclusion, we found little evidence of an increased risk of hip or all fractures with higher intakes of vitamin A or retinol among a cohort of older, postmenopausal women.

Inhalable dust exposures, tasks, and use of ventilation in small woodworking shops: a pilot study.

Measures of workers' inhalable dust exposures, tasks, and ventilation use were made in five small woodworking shops prior to the start of an intervention effectiveness study aimed at lowering personal wood dust exposures. The data were used to (1) design a sampling protocol for an intervention success measure, (2) identify targets for intervention among the tasks and activities responsible for high dust levels, and (3) develop shop-level measures as tools for tailoring intervention activities. Geometric mean dust concentrations ranged from 1.6 to 9.9 mg/m3 in the five shops, with the highest levels occurring in a cabinet shop. All shops had centralized dust collection systems and workers generally used dust control on stationary tools (60-100% of the time) when it was available. Sanding with both stationary and handheld powered tools, cleaning with methods that can disperse dust (e.g., brushes, compressed air), and miscellaneous tasks were all responsible for significant personal exposures. The positive association between miscellaneous tasks and exposures probably reflects the high background levels generated by nearby processes. Sanding with both stationary tools and handheld powered tools represents the most significant influence on personal exposures in small woodworking shops. The authors conclude that pilot studies are useful tools for designing occupational health and safety intervention effectiveness studies.

Designing intervention effectiveness studies for occupational health and safety: The Minnesota Wood Dust Study.

BACKGROUND: A planning model was used to guide the design of a randomized controlled study of the effectiveness of tailored interventions in lowering dust exposures in small woodworking shops. METHODS: Guided by Green's PRECEDE-PROCEED model, we used a planning committee, focus groups and a pilot study to gain information on small woodworking shops, causes of and controls for high dust levels, and barriers and incentives surrounding availability and use of dust controls. RESULTS: The planning committee identified key characteristics of small woodworking shop owners. Focus groups with owners and employees served to further elucidate why dust control was considered unimportant. The pilot study gave measures of dust exposures, tasks, and use of controls. Interventions focused on providing owners with technical and economic assistance to lower dust levels and an educational program for employees discussing health effects and effective methods of dust control. CONCLUSIONS: The PRECEDE-PROCEED model proved a useful framework for designing an intervention in the occupational setting.

Induced abortion and breast cancer risk.

Results from case-control studies suggest that induced abortion may be associated with a small increase in risk of breast cancer. While risk estimates from cohort studies have generally not observed such an association, these studies have had limited information regarding abortion and possible confounding variables. Therefore, we conducted a study among a cohort of post-menopausal women from whom detailed information regarding pregnancy outcomes as well as risk factors for breast cancer had been collected. The study sample included 37,247 Iowa Women's Health Study participants, 55-64 years of age at baseline in 1986, who reported no history of breast, or other, cancer (except non-melanoma skin cancer), and for whom information regarding pregnancy outcomes (that is, live birth, stillbirth, spontaneous abortion, ectopic pregnancy or induced abortion) was available. We used linkage with records of the State Health Registry of Iowa, part of the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program, to estimate the incidence of breast cancer among cohort members through 1995. We calculated age-adjusted relative risks and 95% confidence intervals using Cox proportional hazards regression. Only 653 women (1.8%) reported an induced abortion. The age-adjusted relative risk of breast cancer among women with prior induced abortion compared with those without was 1.1 (95% CI = 0.8-1.6). Relative risks were higher among women whose age at first abortion was less than 20 or at least 30 years, for those whose abortion took place after their first birth or who never gave birth, and for those with early termination (0-2 months). These estimates varied from 1.3-1.7, but the confidence intervals around each were wide. Since most women in this cohort were beyond their reproductive years when abortion became legal in 1973, the low prevalence of induced abortion argues for a cautious interpretation.

Breast conservation therapy in the United States following the 1990 National Institutes of Health Consensus Development Conference on the treatment of patients with early stage invasive breast carcinoma.

BACKGROUND: A National Institutes of Health (NIH) Consensus Development Conference on the treatment of patients with early stage invasive breast carcinoma, held in June 1990, recommended breast conservation therapy for the majority of women with Stage I or II breast carcinoma. The authors evaluated the national use of breast conservation therapy before and after the conference to determine whether the conference had had an impact on utilization. METHODS: Women with Stage I or II breast carcinoma (n = 109,880), diagnosed during the years 1983-1995, were identified via 9 population-based cancer registries of the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute. The likelihood of breast conservation surgery versus mastectomy and, among women who underwent breast conservation surgery, the likelihood of postoperative radiation therapy versus none, were assessed for 3 time periods (January 1983 to April 1985, May 1985 to June 1990, and July 1990 to December 1995). Associations between the use of breast conservation surgery or postoperative radiotherapy according to patient stage, age, race, and region were compared among women diagnosed before and after the NIH Consensus Development Conference. RESULTS: From 1985 (the year that the U.S. randomized controlled trial demonstrating equivalent efficacy between breast conservation therapy and mastectomy was published) through 1989, approximately 35% of women with Stage I and 19% of women with Stage II breast carcinoma underwent breast conservation surgery; these percentages remained constant throughout this period. Beginning in 1990, the year of the NIH Consensus Development Conference, the use of breast conservation surgery increased in each subsequent year; by 1995, 60% of women with Stage I and 39% of women with Stage II breast carcinoma received such treatment. However, regional variation in use was observed (Stage I, range 41.4-71.4% for 1995) and no registry reported breast conservation therapy for the majority of women with Stage II disease (range, 23.8-48.0%). The use of postoperative radiotherapy for women who underwent breast conservation surgery was similar in the periods before and after the conference. CONCLUSIONS: Although breast conservation therapy was performed more frequently following the NIH Consensus Development Conference, variation in use by region of the U.S. suggests the continued presence of barriers to widespread adoption of the recommendations formulated at the conference.

Medical records as an alternative to self-report for measuring mammography utilization.

A pilot study assessed whether medical records were a viable alternative to self-report for measuring mammography use in a population-based sample. Of 98 women contacted by telephone, 62 (63.3%) ultimately provided written consent to obtain their mammogram reports. Although all physicians complied with requests for records, an average of three physician contacts per woman were required and 87 percent of mammogram reports were located; therefore, records were available for only 56 percent of women contacted initially. This, coupled with the effort associated with obtaining the records, does not support the use of medical records as an alternative to self-report to measure mammography utilization in the general population.