Breast cancer: magnitude of the problem and descriptive epidemiology

Breast cancer is the most common cancer among women in the United States. Knowledge of the descriptive epidemiology of breast cancer is useful both in suggesting etiologic hypotheses and, if preventive measures can be identified, in delineating high-risk groups to be targeted for preventive efforts. Demographic risk factors include increasing age (in Western countries), being white for breast cancer diagnosed at age 45 years or more, being black for breast cancer diagnosed at less than 40 years of age, high socioeconomic status, having never married, being of the Jewish faith, urban residence, and residence in the northern (as compared with the southern) United States. Incidence rates are generally highest in North American and Northern European countries, intermediate in Southern and Eastern European and South American countries, and lowest in Asia and Africa. The most notable characteristic of the descriptive epidemiology of breast cancer in recent years is perhaps the rapidly increasing incidence rates in developing countries. Identification of specific reasons for these increasing rates would contribute substantially to our understanding of the epidemiology of breast cancer.

Oral and pharyngeal cancer and occupation: a case-control study

We studied the relation between occupation and oral and pharyngeal cancer with a population-based case-control study conducted in four areas of the United States. The study group included 1,114 incident male and female cases and 1,268 frequency-matched controls. After adjustment for age, race, smoking, alcohol, and study location, an analysis of lifetime occupational histories revealed a small number of noteworthy associations. Risk was increased among male carpet installers (23 cases, 4 controls), with an adjusted odds ratio of 7.7 [95% confidence interval (CI) = 2.4-24.9], and tended to rise with longer duration of employment. A decreased risk was found among male and female textile mill workers (odds ratio 0.48, 95% CI = 0.27-0.88). Previously reported increases in oral cancer risks among printing workers, electrical and electronics workers, and workers other than carpet installers who were possibly exposed to formaldehyde were not found in this study. For several employment groups, including male machinists, primary metal industry workers, petroleum industry workers, painters, furniture and fixture industry workers, woodworking machine operators, and workers with inferred exposure to fossil fuel combustion, odds ratios were approximately 2.0 for cancers of pharyngeal sites.

A case-control study of hip fracture: evaluation of selected dietary variables and teenage physical activity

Recent diet, teenage physical activity and teenage calcium consumption were examined as risk factors for hip fracture in a case-control study. Cases were 161 white women admitted to one of 30 participating hospitals with a first hip fracture. Controls included 168 white women from general and orthopedic surgical services frequency-matched to cases by age group and hospital. Information on exposure to possible risk factors was obtained by in-person interview. No association was found between recent intake of calcium, phosphorus, protein, vitamin C or caffeine and hip fracture. Also, teenage calcium intake and milk drinking were not related to hip fracture risk. Recreational activities in adolescence and early adulthood appeared to afford protection against hip fracture. The highest quartile of recreational activity (greater than or equal to 4 times/week) was associated with an odds ratio of 0.24 (95% confidence interval 0.08-0.75) relative to the lowest quartile (less than 1 time/week).

Risk factors for fractures of the distal forearm and proximal humerus. The Study of Osteoporotic Fractures Research Group

The Study of Osteoporotic Fractures is a prospective cohort study begun in 1986 that includes 9,704 women aged 65 years and older from Maryland, Minnesota, Oregon, and Pennsylvania. A total of 171 women suffered fractures of the distal forearm, and 79 women had fractures of the proximal humerus during the first 2.2 years of follow-up. Most fractures at both sites occurred as a result of a fall. Low bone mineral density was a strong predictor of these fractures; comparing those in the lowest quintile of bone mineral density in the distal radius with those in the highest quintile, the rate ratio was 4.1 for fractures of the distal forearm and 7.5 for fractures of the proximal humerus. Other factors associated with an increased rate of distal forearm fracture independently of low bone mineral density included poor visual acuity, number of falls in the year before baseline, and frequent walking. Factors that appeared to be independently associated with an increased rate of fracture of the proximal humerus included a recent decline in health status, insulin-dependent diabetes mellitus, infrequent walking, and several indicators of neuromuscular weakness such as inability to stand with feet in a tandem position for more than a few seconds. These data support the hypothesis that distal forearm fractures often occur as a result of a fall in women with low bone mineral density who are relatively healthy and active and have good neuromuscular function, while fractures of the proximal humerus tend to occur as a result of a fall in women with low bone mineral density who are less healthy and less active than average and who have poor neuromuscular function.

Evaluation of random digit dialing as a method of control selection in case-control studies

Control groups selected by random digit dialing are frequently used in case-control studies. Concern about the potential for bias in these control groups has been expressed, primarily because of low response rates. This study compares the characteristics of a hypothetical control group consisting of 341 men and women aged 40-74 years, selected by random digit dialing and participating in an interview in 1990, with the characteristics of 15,563 men and women aged 40-74 years who participated in a privately conducted census in the same upstate New York county in 1989. For most measures, no differences were seen between the random digit dialing sample and the census population. However, the hypothetical control group was more likely to have had their cholesterol checked in the past 2 years and was somewhat more likely to have had other screening tests as well. In addition, the hypothetical control group was somewhat better educated. The results suggest that, at least in this setting, control groups selected by random digit dialing are representative of the general population in most respects; however, caution should be used when studying the relation between screening tests and disease occurrence by means of case-control studies using controls selected by random digit dialing.

Medications and multiple falls in elderly people: the St Louis OASIS study

The purpose of this study was to identify associations between the use of commonly taken medications and groups of medications and the risk of falls in elderly people living in the community. A stratified random sample of 1358 persons aged 65 years and over was selected from the 15,000 members of an educational organization for functionally independent, community-dwelling elderly people in St Louis, Missouri. Twenty-seven per cent of subjects reported at least one fall in the past year and 8% reported two or more falls. After adjusting for potential confounders (including age, sex, relevant medical conditions, health status, cognitive impairment, use of alcohol, depression and use of other medications), the following medications were found to be important risk factors for multiple falls: diazepam [odds ratio (OR): 3.7, 95% confidence interval (CI): 1.5-9.3], diltiazem (OR: 1.8, 95% CI: 0.8-4.1), diuretics (OR: 1.8, 95% CI: 1.2-2.8) and laxatives (OR: 2.1, 95% CI: 1.0-4.5). We conclude that caution is needed before prescribing diuretics and psychotropics, especially diazepam, for elderly people. The safety of diltiazem in this age group should be assessed further.

Incidence of hip fractures in the elderly: a cross-national analysis

This paper reviews international data on incidence rates of hip fracture in persons 50 years of age and older, based on a bibliographic search of articles published since 1960. Incidence rates are higher in white populations than in black, Asian, and Hispanic populations. In both sexes and in all ethnic groups and geographic areas, incidence rates increase markedly with age. The steep increase with age, however, occurs later in black, Asiatic and Hispanic populations than in whites. The ratio of female to male incidence rates is higher than 1.0 in whites, while in blacks and Asians it has often been the reverse, with higher rates among men. In recent years in Hong Kong incidence rates in females have increased more rapidly than incidence rates in males, so that now the incidence rates in females are higher than those in males. In addition to the study in Hong Kong, most studies in Northern Europe and North America show an increase in age-adjusted hip fracture incidence rates over time over the past few decades. Methodological differences among the various studies (including differences in the definition of hip fracture, in case ascertainment, and in the selection and sample size of the study population) necessitate cautious interpretation of the findings of this report.

Risk factors for falls as a cause of hip fracture in women. The Northeast Hip Fracture Study Group

BACKGROUND

Although even in the elderly most falls are not associated with fractures, over 90 percent of hip fractures are the result of a fall. Few studies have assessed whether the risk factors for falls are also important risk factors for hip fracture.

METHODS

To examine the importance of risk factors for falls in the epidemiology of hip fracture, we performed a case-control study of 174 women (median age, 80 years) admitted with a first hip fracture to 1 of 30 hospitals in New York and Philadelphia. Controls, matched to the case patients according to age and hospital, were selected from general surgical and orthopedic surgical hospital services. Information was obtained by direct interview.

RESULTS

As measured by the odds ratio, increased risks for hip fracture were associated with lower-limb dysfunction (odds ratio = 1.7; 95 percent confidence interval, 1.1 to 2.8), visual impairment (odds ratio = 5.1; 95 percent confidence interval, 1.9 to 13.9), previous stroke (odds ratio = 2.0; 95 percent confidence interval, 1.0 to 4.0), Parkinson's disease (odds ratio = 9.4; 95 percent confidence interval, 1.2 to 76.1), and use of long-acting barbiturates (odds ratio = 5.2; 95 percent confidence interval, 0.6 to 45.0). Of the controls, 44 (25 percent) had had a recent fall. The case patients were more likely than these controls to have fallen from a standing height or higher (odds ratio = 2.4; 95 percent confidence interval, 1.0 to 5.7). Of those with hip fracture the younger patients (less than 75 years old) were more likely than the older ones (greater than or equal to 75 years old) to have fallen on a hard surface (odds ratio = 1.9; 95 percent confidence interval, 1.04 to 3.7).

CONCLUSIONS

A number of factors that have been identified as risk factors for falls are also associated with hip fracture, including lower-limb dysfunction, neurologic conditions, barbiturate use, and visual impairment. Given the prevalence of these problems among the elderly, who are at highest risk, programs to prevent hip fracture should include measures to prevent falls in addition to measures to slow bone loss.

The epidemiology of breast cancer

Table 5 presents risk factors for breast cancer generally regarded as established, together with their approximate relative risks. With the exception of age, country of birth, and a history of breast cancer in both a mother and a sister, all of the relative risks reported to date are of a relatively modest magnitude. Thus, new risk factors need to be identified and knowledge of existing risk factors refined. Factors for which the evidence of an etiologic role has mounted over the past several years, but which are not yet considered to be established, include the protective effects of parity and lactation in certain age groups and the increased risks associated with alcohol consumption and with DES exposure during pregnancy. In addition, physical activity has emerged as a factor worthy of further study. Some evidence suggests that use of oral contraceptives for several years at an early age modestly increases the risk for breast cancer diagnosed before age 35 and perhaps age 45. Use of estrogen-replacement therapy for 20 years or more has been found by a few studies to increase the risk for breast cancer in the postmenopausal years; further studies of very long-term users are needed. Also, other risks and benefits of these hormones need to be taken into account when women decide whether to use them. Surprisingly elusive has been the etiologic role of endogenous hormones, especially in view of the large number of studies that have been concerned with them. A better understanding of the role of endogenous hormones should help explain the mechanisms of action of known and suspected risk factors. Areas of high priority for further research thus include establishing with more certainty whether the risk for breast cancer is increased in any subgroups of women who use oral contraceptives and estrogen-replacement therapy and determining the etiologic roles of specific endogenous hormones. The possible risks associated with alcohol consumption and lack of physical activity need to be studied more thoroughly, and ideas about new potential risk factors are needed. Although epidemiologic studies will continue to be concerned with diet, enthusiasm for its etiologic role in women has been considerably dampened by the lack of association in many of the studies reported to date. The studies in women exposed to radiation, DES, and oral contraceptives suggest that the timing of some exposures may be critical, since the effects of these agents may mostly be limited to specific time periods of rapid breast development.(ABSTRACT TRUNCATED AT 400 WORDS)

Familial aggregation of Paget's disease of bone

This epidemiologic study of Paget's disease of bone used data from 788 cases and 387 spouse controls to investigate the following: (1) the extent to which this disorder aggregates in families; (2) the cumulative incidence of the disease in first-degree relatives of patients throughout life; and (3) the influence of age at diagnosis (less than 55 versus 55+ years) and presence of bone deformity in the case on risk of Paget's disease in relatives. A positive family history in parents or siblings was reported by 12.3% of cases and 2.1% of controls. The rate of Paget's disease was approximately seven times as high in relatives of cases as in relatives of controls, and this increased rate did not differ according to gender of case or control or gender of relatives. Cumulative incidence of Paget's disease to age 90 was much higher in relatives of cases (8.9 +/- 1.0% SEM) than in relatives of controls (1.8 +/- 0.9% SEM). Among relatives of cases, cumulative risk was highest when the case had both early age at diagnosis and bone deformity (20.7 +/- 3.6% SEM) compared with risk when the case had early age at diagnosis but not bone deformity (10.8 +/- 3.2% SEM), bone deformity but not early age at diagnosis (5.8 +/- 1.3% SEM), or neither bone deformity nor early age at diagnosis (3.6 +/- 0.8% SEM). Risk in siblings of cases was higher when a parent was affected (22.1 +/- 8.0% SEM) than when both parents were unaffected (6.7 +/- 1.1% SEM).(ABSTRACT TRUNCATED AT 250 WORDS)

Familial predisposition for herniation of a lumbar disc in patients who are less than twenty-one years old

The parents of sixty-three patients who were less than twenty-one years old and who had operatively confirmed herniation of a lumbar disc were interviewed regarding a history of sever back pain, sciatica, and herniated disc, to determine whether aggregation of herniation of a lumbar disc occurs in families of patients in this young age-group. The parents of sixty-three additional patients who had a non-spinal orthopaedic diagnosis (control group) were matched for age and sex with the study group and were given the same interview. Of the patients who had herniation of a lumbar disc and were less than twenty-one years old, 32 per cent had a positive family history for that lesion compared with 7 per cent of the control group. The relative risk of development of herniation of a lumbar disc before the age of twenty-one years is estimated to be approximately five times greater in patients who have a positive family history. The results indicate a familial basis for herniation of a lumbar disc in patients who are less than twenty-one years old.

Methodologic issues in the study of frequent and recurrent health problems. Falls in the elderly

In this paper the example of falls in the elderly is used to demonstrate methodologic difficulties that arise in the epidemiologic study of frequent and recurrent health problems. Issues discussed include whether the relevant outcome is the state of being a faller or the rate at which falls occur, misclassification of self-reported outcome data, the inadequacies of current terminology for describing certain study types and measures of frequency and effect from studies of recurrent events, the potential for outcome to influence exposure status in cohort studies of recurrent health problems, and the question of controlling for falls occurring prior to the study period. It is concluded that epidemiology needs to develop a framework for studying frequent and recurrent health problems.

Low back pain/prolapsed lumbar intervertebral disc

Low back pain is common throughout the adult years in both men and women; first episodes most frequently occur among people in their 20s and 30s. Prolapsed lumbar disc most often affects individuals in the age range 25-45 years; prolapses occur infrequently in persons below 20 years or over 65 years. Major risk factors for low back pain in general and for prolapsed disc specifically include frequent lifting of objects weighing 25 pounds or more, especially if the objects are lifted with the arms extended and with the knees straight and if the lifting is done while the body is twisted; exposure to whole-body vibration, including driving motor vehicles; cigarette smoking; and, for prolapsed lumbar disc, narrow lumbar vertebral canals. Possible risk factors for which the evidence is weak or inconsistent include frequent stretching, reaching, pulling, and pushing on the job; sedentary occupations; jobs in which workers stay in one position for long periods of time; recent employment in a physically demanding job; jobs requiring frequent twisting without lifting; tallness; heredity; extent of forward flexibility in the lumbar area; lack of physical fitness; pregnancies; psychological symptoms; and frequent participation in bowling. The methods suggested to date with the greatest potential for prevention include modification of jobs so as to reduce exposure to known occupational risk factors, and careful selection of workers by such means as strength testing for the particular job for which they are to be employed.

Paget's disease of bone and previous pet ownership in the United States: dogs exonerated

Paget's disease of bone is currently believed to be the result of a paramyxovirus infection of osteoclasts. Previously reported immunohistological data have suggested that a virus resembling either the measles virus or a respiratory syncytial virus is the probable causative agent, but no organism has been isolated or definitively identified to date. A recent study reporting an increased exposure to dogs during childhood and adolescence in a small series of cases from the North West of England proposed that a canine virus, possibly distemper, might be the primarily infectious agent. To study this hypothesis further, we examined prior dog and cat ownership from childhood through adulthood in 433 cases of Paget's disease and an equal number of matched controls living in the US. We found no differences related to prior pet ownership. We conclude that past dog (or cat) ownership is not a risk factor for the development of Paget's disease.

Scientific standards of criticism: a reaction to "Scientific standards in epidemiologic studies of the menace of daily life," by A.R. Feinstein

Feinstein's criticism of epidemiology are summarized and evaluated. His major premises appear to be that methodologic errors inevitably result in false positive associations, that epidemiologists are complacent about methodology, and that epidemiologists encourage overinterpretation of epidemiologic data by the public. We challenge these premises and discuss a number of technical errors that underlie Feinstein's writings: he generally ignores the tendency of nondifferential exposure misclassification to dilute associations; he inappropriately interchanges measure of disease occurrence, which leads him to erroneous assertions regarding differences among studies; and he asserts that absence of a dose-response gradient precludes causality, despite the fact that causal effects need not follow a monotonic dose-response curve over the entire range of exposure. We also challenge his assertions that contradictory results necessarily indicate poor study methods and that prior beliefs of the data collectors inevitably affect study results in ways not apparent in the study methods. Feinstein's approach to the use of epidemiology in policy formulation ignores the need to weigh all evidence and distinguish important from unimportant biases. We illustrate this point by documenting how the use of Feinstein's "scientific standards" in evaluating the evidence linking aspirin to Reye's syndrome would have led to costly errors in medical practice.

Cervical intraepithelial neoplasia among women with papillomavirus infection compared to women with Trichomonas infection

This study was undertaken to determine if women with papillomavirus infection were more likely to develop cervical intraepithelial neoplasia (CIN) than women with other sexually transmitted infections. Women with cytologic evidence of papillomavirus infection and a comparison group of women with cytologic evidence of Trichomonas infection were identified from a reexamination of cervicovaginal smears initially evaluated between 1973 and 1981 in a private pathology laboratory. To identify subsequent CIN among these women the authors reviewed records of private obstetric and gynecology practices and public clinics through 1983. After accounting for possible confounding variables, including age, marital status, frequency of cervical cytologic examination, and selected characteristics of pregnancy history, a 2.7-fold increase in the rate of CIN was found among the 613 women with prior papillomavirus infection compared to the 410 women with previous Trichomomas infection. The rate ratio was higher among women with more severe cervical neoplasia than for those with less severe neoplasia and for those followed for greater than 12 months than for those followed 7 to 12 months. The results of this study provide further evidence of the role of papillomavirus in the etiology of cervical cancer.