Electric blanket use and breast cancer risk among younger women

To investigate whether use of electric blankets, one of the largest sources of electromagnetic field exposure in the home, is associated with the risk of female breast cancer, the authors analyzed data from a population-based US case-control study. The 2,199 case patients were under age 55 years and had been newly diagnosed with breast cancer between 1990 and 1992. The 2,009 controls were frequency-matched to cases by 5-year age group and geographic area. There was little or no risk associated with ever having used electric blankets, mattress pads, or heated water beds among women under age 45 years (adjusted odds ratio = 1.01, 95% confidence interval 0.86-1.18) or among women aged > or =45 years (adjusted odds ratio = 1.12, 95% confidence interval 0.87-1.43). There was no substantial variation in risk with duration of use; with whether the appliance was used only to warm the bed or used throughout the night; with menopausal status; or with the cases' hormone receptor status or stage of disease. Potential breast cancer risk factors that were associated with electric blanket use did not substantially confound the associations under investigation. These data do not support the hypothesis that electric blanket use increases breast cancer risk among women under age 55 years.

Recreational physical activity and breast cancer risk among women under age 45 years

To evaluate whether recreational physical activity is associated with breast cancer among young women, the authors analyzed data from a population-based case-control study. Cases (n = 1,668) were women under age 45 years who had been newly diagnosed with breast cancer between 1990 and 1992 in Atlanta, Georgia, central New Jersey, or Seattle, Washington. Controls (n = 1,505) were frequency-matched to cases by 5-year age group and geographic area of residence. Breast cancer was not associated with recreational activity in any of the three time periods assessed (highest quartile of activity vs. lowest: age- and center-adjusted odds ratio (OR) = 0.94 (95% confidence interval (CI) 0.77-1.15) at ages 12-13 years, OR = 1.08 (95% CI 0.88-1.32) at age 20 years, and OR = 1.18 (95% CI 0.97-1.44) during the past year), with the average of the three time periods (OR = 1.02, 95% CI 0.84-1.25), or with daily climbing of at least two flights of stairs (without stopping) during the past year (daily climbing vs. never climbing: OR = 1.03, 95% CI 0.86-1.23). Estimates were not modified or confounded by body mass index, menopausal status, or caloric intake during the past year. These results do not support a protective role for physical activity in the risk of breast cancer among young women.

Characteristics of falls and risk of hip fracture in elderly men

The steep rise in hip fracture incidence rates with age is not fully explained by an increase in the frequency of falls or by reduction in bone mineral density, suggesting that circumstances of falls may also affect the risk of hip fracture. Previous studies conducted mainly among women have identified the importance of the orientation of a fall in the etiology of hip fracture. In this case-control study among men of 45 years and older, we evaluated how the circumstances of falls affect the risk of hip fracture. We compared 214 cases with hip fracture due to a fall with 86 controls who had fallen within the past year but did not sustain a hip fracture. As expected, in multivariable age-adjusted analyses men who reported hitting the hip/thigh in a fall had a markedly elevated risk of hip fracture (OR = 97.8; 95% CI = 31.7-302). Hitting the knee in a fall was associated with reduced risk (OR = 0.24; 95% CI = 0.09-0.67). Other factors that were associated with reduced risk of hip fracture among men who fell were more hours of physical activity in the past year (OR = 0.84; 95% CI = 0.73-0.97, for each additional 4 h per week), a greater body mass index (OR = 0.60; 95% CI = 0.40-0.90, for each additional 4 kg/m2), and a history of a fracture when age 45 years or older (OR = 0.26; 95% CI = 0.10-0.69). Reported lower limb dysfunction was associated with increased risk of hip fracture (OR = 6.41; 95% CI = 2.09-19.6) among fallers. The increased risk associated with hitting the hip/thigh in a fall and the reduced risk associated with high body mass index suggest that preventive efforts for older men at high risk might include protective hip pads to reduce the force on the hip in a fall. Exercise and strength training programs may also reduce the risk of hip fracture among men who fall.

Regional differences in known risk factors and the higher incidence of breast cancer in San Francisco

BACKGROUND

The age-adjusted incidence of breast cancer in the San Francisco Bay Area has consistently been higher than that in other regions of the United States. The distribution of established risk factors for breast cancer (i.e., parity, age at first full-term pregnancy, breast-feeding, age at menarche, and age at menopause) and probable risk factors (e.g., alcohol consumption) also differs across geographic regions.

PURPOSE

A study was planned to explore the extent to which differences in the regional distribution of established and probable risk factors could explain the increased incidence of breast cancer in the San Francisco Bay Area.

METHODS

Age-adjusted breast cancer incidence rates for January 1978 through December 1982 were obtained for the San Francisco Bay Area and other regions from the Surveillance, Epidemiology, and End Results (SEER) Program. Risk factor data from January 1980 through December 1982 were computed from the Cancer and Steroid Hormone Study, a population-based, case-control study of women 22-55 years of age who resided in eight SEER regions. Two different statistical methods were used to compute the relative risk (RR) of breast cancer associated with residence in the San Francisco Bay Area versus other regions, after adjusting for regional differences in known risk factors.

RESULTS

Substantial differences in the distribution of breast cancer risk factors were found between the San Francisco Bay Area and other regions. Nearly all of these differences would be expected to lead to an elevated incidence of breast cancer in the San Francisco Bay Area. With the use of incidence rates adjusted only for age, the RR for San Francisco Bay Area residence from January 1978 through December 1982 compared with residence in seven other SEER areas was 1.14 for white women and 1.10 for black women. Depending on the statistical method used, the RR was reduced to approximately 0.96-0.99 for white women and 0.75-0.83 for black women, after further adjusting for established and probable risk factors (parity, age at first full-term pregnancy, breast-feeding, age at menarche, age at menopause, and alcohol consumption). Without adjustment for alcohol consumption, the corresponding results were 0.97-1.02 for white women and 0.77-0.88 for black women.

CONCLUSIONS

Among both white women and black women, the elevated breast cancer incidence rate in the San Francisco Bay Area can be completely accounted for by regional differences in known risk factors.

Risk factors for hip fracture in men. Hip Fracture Study Group

To identify risk factors for hip fracture in men, the authors conducted a case-control study involving 20 hospitals in Philadelphia, Pennsylvania, and 14 hospitals in Kaiser Permanente Medical Care Program of northern California. The 356 enrolled men had been admitted with a radiologically confirmed first hip fracture. The 402 control men either were from the Philadelphia area or were members of Kaiser Permanente and were frequency matched to the cases by age and ZIP code or telephone exchange. Information on potential risk factors was obtained through personal interviews. Men in the lowest quintile of body mass had a greatly increased risk of hip fracture compared with men in the heaviest quintile (odds ratio (OR) 3.8, 95% confidence interval (CI) 2.3-6.4). Premorbid lower limb dysfunction was associated with increased risks for hip fracture (OR 3.4, 95% CI 2.1-5.4). Increased risks were also observed with the use of cimetidine (OR 2.5, 95% CI 1.4-4.6) and psychotropic drugs (OR 2.2, 95% CI 1.4-3.3). Smoking cigarettes or a pipe increased the risk of hip fracture, and this association was independent of body mass. Finally, previous physical activity was markedly protective. Factors thought to affect bone density as well as factors identified as risk factors for falls appear to be important determinants of the risk of hip fracture in men. Physical activity may be a particularly promising preventive measure for men. Additional studies of the use of cimetidine on osteoporosis and osteoporotic fractures are indicated.

Hospital controls versus community controls: differences in inferences regarding risk factors for hip fracture

In case-control studies using cases identified from persons admitted to hospitals, two types of controls are most often used: persons from the communities served by the hospitals and persons admitted to the same hospitals as those to which the cases were admitted. It is often unclear which is the more appropriate choice, and whether the use of one or the other type of control group will lead to biased conclusions. The purpose of the present analysis was to determine whether the choice of hospital controls versus community controls would influence conclusions regarding risk factors for hip fracture. Cases (n = 425), hospital controls (n = 312) and community controls (n = 454) were drawn from a case-control study of risk factors for hip fracture in women. Study participants were white and black women aged 45 years or older and living in New York City or Philadelphia, Pennsylvania, who were selected between September 1987 and July 1989. Using community controls but not hospital controls, investigators would have concluded that having a fall during the previous 6 months, current smoking, and moving during the previous year were associated with an increased risk of hip fracture. Associations of hip fracture risk with stroke and prior use of ambulatory aids were stronger using community controls, but associations with estrogen use and body mass index were not influenced by choice of control group. Community controls were quite similar to representative samples of community-dwelling elderly women, whereas hospital controls were somewhat sicker and more likely to be current smokers. The authors conclude that community controls comprise the more appropriate control group in case-control studies of hip fracture in the elderly.

Vitamin D receptor polymorphisms, bone mineral density, and bone metabolism in postmenopausal Mexican-American women

Common polymorphisms in the vitamin D receptor (VDR) gene have been shown to correlate with bone mineral density (BMD). However, attempts to replicate the original findings in other populations have yielded variable results. These disparities may reflect ethnic or environmental differences in the expression of the VDR effect upon BMD. We examined a relatively ethnically homogeneous group of 103 healthy postmenopausal Caucasian women of Mexican descent living in Northern California. We determined the VDR genotype and measured the BMD at the lumbar spine and femoral neck by dual-energy X-ray absorptiometry, as well as several biochemical indices of mineral metabolism. The prevalence of the BB genotype, associated in previous studies with the lowest BMD, was 8% and highly linked to the tt genotype. Absolute and age-adjusted BMD at both hip and spine showed a trend toward lower BMD in the BB, AA, and tt genotypes, but this trend did not achieve statistical significance. There were no consistent intergroup differences in change in BMD over 2 years of follow-up, nor in mean serum concentrations of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, osteocalcin, or total urinary pyridinolines. Intact parathyroid hormone concentrations were significantly higher in subjects with the AA genotype, with a trend toward higher values in those with the BB and tt genotypes as well. Our data suggest that there may be a decrease in BMD associated with the B, A, and t alleles, but the intergroup difference in BMD is 0.2-0.5 standard deviations (SD) at the lumbar spine and 0.3 SD at the femoral neck, decreases that are smaller than previously reported. Given the relatively low prevalence of the BB/tt genotype in Mexican-American Caucasians, a larger sample would be required to detect a significant association between VDR alleles and differences in BMD of the magnitude suggested by our data. We conclude that a genotype effect of this magnitude, if present, would be clinically relevant, but the impact on BMD is too small to detect with statistical significance in a study of this size.

Associations of vitamin C, calcium and protein with bone mass in postmenopausal Mexican American women

We investigated the associations of vitamin C, calcium and protein intakes with bone mass at the femoral neck and lumbar spine in postmenopausal Mexican American women. Bone mass was measured by dual-energy X-ray absorptiometry (DXA) and expressed as areal (BMD, g/cm2) and volumetric (bone mineral apparent density or BMAD, g/cm3) bone mineral density. Diet was assessed using a modified version of the National Cancer Institute Food Questionnaire, which was administered by trained bilingual interviewers familiar with Mexican dietary practices. Data gathered from 125 subjects were analyzed using multiple linear regression analysis with age, body mass index (BMI), acculturation, years of estrogen use, physical activity, total energy intake, and the nutrient of interest as independent variables. Neither calcium nor calcium/protein ratio was associated with bone mineral density. There was evidence of a positive association between dietary vitamin C intake and femoral neck BMD (beta = 0.0002 g/cm2 per mg/day, SE = 0.00006, p < 0.05), but vitamin C was not associated with lumbar spine bone mass. Further investigation of the role of vitamin C in skeletal health is warranted.

Epidemiology and prevention of breast cancer

Breast cancer is the most common cancer in women, accounting for 32% of all newly diagnosed cancers. Demographic characteristics associated with an increased risk include increasing age, birth in North America or northern Europe, high socioeconomic status, never having been married, and, for breast cancer diagnosed after 45 years of age, the white race. Early age at menarche, late age at menopause, late age at first full-term pregnancy, and low parity increase risk, while removal of the ovaries at an early age is protective. Obesity increases risk in postmenopausal women. Having a first degree relative with breast cancer confers an increased risk, especially if both a mother and a sister have had breast cancer at an early age. Mutations in the BRCA1 and BRCA2 genes are associated with an inherited susceptibility to breast cancer at an early age. Other markers of increased risk include atypical and hyperplastic epithelial cells in nipple aspirate fluid, nodular densities on mammogram, and biopsy-confirmed benign proliferative breast disease. Little can be done at present to reduce breast cancer risk through primary prevention, but secondary prevention by mammographic screening in women of age 50 and older reduces mortality from breast cancer.

Non-syncopal falls in the elderly in relation to home environments

Methods of prevention of falls in the home may differ for healthy and frail individuals. We therefore sought to determine whether measures of health and functioning in older persons are more useful in predicting falls at home not involving home hazards (non-environmental falls) than falls at home related to home hazards (environmental falls), and whether these relationships differ among those who fell once and those who fell multiple times during follow-up. Data for this analysis are from a 1-year prospective cohort study of 325 community-dwelling volunteers aged 60-93 years who had fallen during the year before baseline. In general, associations were stronger between poor functional ability and non-environmental falls than between poor functional ability and environmental falls. Independent predictors of non-environmental first falls during follow-up included Parkinson's disease (adjusted odds ratio (AOR) 7.66, 95% confidence interval (95% CI) 1.15-51.1) and being home alone 10 or more hours per day (AOR 2.36, 95% CI 1.20-4.61); independent predictors of environmental first falls during follow-up included arthritis (AOR 2.60, 95% CI 1.32-5.09) and poor depth perception (AOR 0.73, 95% CI 0.59-0.89, for each unit increase in depth perception score). Also, associations between poor function and falls were generally stronger among participants who fell repeatedly than among individuals who fell only once during the follow-up year. In conclusion, poor function predisposes to non-environmental falls at home in older persons and, to a lesser extent, environmental falls in those who fall repeatedly. Certain functional characteristics such as poor depth perception may predispose to environmental falls to a greater extent than do other disabilities.

Factors contributing to skeletal health of postmenopausal Mexican-American women

Incidence rates of hip fracture are lower in Hispanic (HC) than non-Hispanic Caucasians (NHC). To investigate factors that may affect skeletal health of Hispanics, we recruited 152 healthy community-dwelling Mexican-American Caucasian women into a 4-year longitudinal study that evaluates bone mass, nutritional status, muscle strength, mobility, falls, and other factors that may contribute to fracture risk. Results from the baseline component of the study are reported herein. Average bone mineral densities (BMD) evaluated by dual-energy X-ray absorptiometry (DXA) in this study group did not differ from BMDs in healthy, NHC women of similar age. Hip axis length (HAL), however, was significantly shorter than that reported for nonosteoporotic NHC. Factors independently associated with greater BMD and BMC at certain skeletal sites were lean body mass, fat mass, acculturation, years of estrogen use, sun exposure, hip adductor strength, grip strength, erythrocyte folate, and serum glucose concentrations. Factors independently associated with lower BMD and BMC at certain skeletal sites were age, parity, and vertebral deformities (all p < 0.05). Thus, the decreased risk of hip fracture in HC compared with NHC does not appear to be due to high bone mass. However, other factors such as HAL and body composition may play a role in maintenance of skeletal integrity.

Home hazards and falls in the elderly: the role of health and functional status

OBJECTIVES

This study was undertaken to determine whether vigorous and frail older people who identify environmental hazards in their homes have an increased risk for falls.

METHODS

A 1-year prospective study was conducted among 266 female and 59 male community-dwelling volunteers aged 60 to 93 years who had fallen at least once during the previous year. Composite measures of home safety and of frailty were derived using principal components analysis. Participants were divided into vigorous and frail groups, and associations between baseline home safety measures and falls at home over the follow-up year were compared between the two groups.

RESULTS

Frail individuals were more than twice as likely as vigorous individuals to fall during follow-up (rate ratio [RR] = 2.24; 95% confidence interval [CI] = 1.54, 3.27). In the study group as a whole, falls were not strongly associated with the presence of home hazards. However, when compared with vigorous older persons living with fewer home hazards, vigorous older persons living with more home hazards were more likely to fall. The increased risk for falls among vigorous elderly was limited to falls where home hazards were present. By contrast, living with more home hazards was not associated with increased likelihood of falls among frail older persons.

CONCLUSIONS

While frail older persons experience higher overall fall rates, vigorous older persons should not be overlooked in fall prevention projects.

Teenage and current calcium intake are related to bone mineral density of the hip and forearm in women aged 30-39 years

The relation between diet and bone mineral density in premenopausal women was evaluated in a cross-sectional study of 139 women aged 30-39 years. The population consisted of volunteers recruited in Rockland County, New York, between September 1988 and August 1992. A food frequency questionnaire was used to determine nutrient intake for both the year prior to bone density measurement and for ages 13-17 years. Physical measurements included height, weight, grip strength, and percent body fat. Bone mineral density was measured in the lumbar spine, hip, and forearm. Multiple regression equations were used to relate nutrient intake to bone density while controlling for age, height, weight, and grip strength. There were no relations between lumbar spine or distal forearm bone density and any nutrient studied from either the current or teenage diet. Current dietary calcium intake was modestly related to hip bone density (beta = 0.077; p = 0.074). When fiber intake was added to the multiple regression model, the association between calcium and hip bone density was strengthened (beta = 0.101; p = 0.037); this would be expected, because fiber interferes with calcium absorption. In the teenage diet, phosphorus and calcium intake were related to hip bone density. A higher lifetime calcium intake was associated with a higher hip bone density compared with low lifetime calcium intake. An increase in teenage calcium intake from 800 to 1,200 mg per day is estimated to increase hip bone density by 6 percent.

Risk factors for hip fracture in black women. The Northeast Hip Fracture Study Group

BACKGROUND

Although more than 1 percent of black women 80 years of age or older have hip fractures each year, little is known about risk factors for hip fracture in these women.

METHODS

We carried out a case-control study involving 144 black women admitted with a first hip fracture to 1 of 30 hospitals in New York and Philadelphia. The control were 218 black women living in the community who were matched to the case patients according to age and ZIP Code or telephone exchange and 181 hospitalized black women matched according to age and hospital. Information was obtained through personal interviews and was studied by multivariable logistic-regression analysis.

RESULTS

When the case patients were compared with the control subjects from the community, the women in the lowest quintile for body-mass index had a markedly increased risk of hip fracture as compared with the women in the highest quintile (odds ratio, 13.5; 95 percent confidence interval, 4.2 to 43.3). Postmenopausal estrogen therapy for one year or more was protective for women under 75 years of age (odds ratio, 0.1; 95 percent confidence interval, < 0.1 to 0.5). Factors associated with an increased risk of hip fracture included a history of stroke (odds ratio, 3.1; 95 percent confidence interval, 1.2 to 8.1), use of aids in walking (odds ratio, 5.6; 95 percent confidence interval, 2.7 to 11.5), and consumption of seven or more alcoholic drinks per week (odds ratio, 4.6; 95 percent confidence interval, 1.5 to 14.1). The results were similar when the case patients were compared with the hospitalized control subjects.

CONCLUSIONS

Among black women thinness, previous stroke, use of aids in walking, and alcohol consumption are associated with an increased risk of hip fracture. Postmenopausal estrogen therapy protects against hip fracture in women under 75 years of age.

Epidemiology and primary prevention of cancers of the breast, endometrium, and ovary. A brief overview

Cancers of the breast, endometrium, and ovary account for 41% of incident cancers among women. Many risk factors for breast cancer have been identified, but most are associated with only modest elevations in risk. Also, of all the risk factors identified, few are likely to be affected by intervention programs. The pathogenesis of breast cancer is not well understood, but estrogen and possibly estrogen plus progesterone are likely to be etiologically involved. For endometrial cancer, a major etiologic pathway is exposure to estrogen without cyclic exposure to progesterone. Most of the established risk factors for endometrial cancer appear to affect risk at least in part through this pathway. Only a few risk factors for ovarian cancer have been identified. The two most commonly suggested etiologic mechanisms for ovarian cancer are (a) that suppression of ovulation reduces risk and (b) that suppression of pituitary gonadotropins reduces risk. Each hypothesis is consistent with some, but not all, of the data. Prospects for the primary prevention of these cancers are discouraging at present because few of the risk factors identified to date are readily subject to modification, especially for breast cancer, and the underlying etiologies of these cancers are not well understood, particularly for breast and ovarian cancers.

Characteristics of a hypothetical group of hospital controls for a case-control study

In case-control studies in which cases are ascertained from hospitals, controls are frequently chosen from among patients with other diseases at the same hospitals. This study was undertaken to examine the extent to which a hospital control group is representative of the population to which inferences are made. A hypothetical hospital control group was assembled consisting of 233 men and women aged 40-74 years who were surgical inpatients at the two hospitals in Otsego County, New York, in 1990. The characteristics of this group were compared with the characteristics of 15,563 men and women aged 40-74 years who participated in a privately conducted health census in the same county in 1989 with the use of health-related data collected in the census. In this rural setting, only small differences were found between the hospital control group and the census population on most of the measures considered, including demographic characteristics, certain health behaviors, and the prevalence of common conditions. However, the female hospital controls were more likely to be overweight than the females enumerated in the census, and the men were more likely to have ever smoked cigarettes. These differences were large enough to lead to different interpretations about the strength of the associations between these variables and case-control status.

An epidemiologic study of sports and weight lifting as possible risk factors for herniated lumbar and cervical discs. The Northeast Collaborative Group on Low Back Pain

The associations between participation in several specific sports, use of free weights, and use of weight lifting equipment and herniated lumbar or cervical intervertebral discs were examined in a case-control epidemiologic study. Specific sports considered were baseball or softball, golf, bowling, swimming, diving, jogging, aerobics, and racquet sports. Included in the final analysis were 287 patients with lumbar disc herniation and 63 patients with cervical disc herniation, each matched by sex, source of care, and decade of age to 1 control who was free of disc herniation and other conditions of the back or neck. Results indicated that most sports are not associated with an increased risk of herniation, and may be protective. Relative risk estimates for the association between individual sports and lumbar or cervical herniation were generally less than or close to 1.0. There was, however, a weak positive association between bowling and herniation at both the lumbar and cervical regions of the spine. Use of weight lifting equipment was not associated with herniated lumbar or cervical disc, but a possible association was indicated between use of free weights and risk of cervical herniation (relative risk, 1.87; 95% confidence interval, 0.74 to 4.74).

Parity, lactation and hip fracture

The relationship between parity, lactation and the occurrence of hip fracture was investigated in a case-control study of white women. The cases were patients (n = 174) aged 45 years and over with a radiologically confirmed first hip fracture sampled from among admissions to 30 hospitals in New York and Philadelphia between September 1987 and July 1989. Controls (n = 174) were selected from general surgical and orthopedic services during the same time period and were frequency-matched to cases by age and hospital. Ever having a live birth was associated with reduced odds of hip fracture, controlling for age and hospital of recruitment (odds ratio = 0.65; 95% confidence interval = 0.41-1.04). When body mass index was also controlled, each birth was associated on average with a 9% reduction in the odds of hip fracture (odds ratio = 0.92 [0.78-1.08]), although the trend was not statistically significant. After adjusting for number of births, lactation was not associated with hip fracture (adjusted odds ratio for 12 months of lactation or less = 0.80 [0.42-1.55]; adjusted odds ratio for more than 12 months = 1.08 [0.45-2.60]).

Number of pregnancies and the subsequent risk of cardiovascular disease

BACKGROUND

Whether increasing parity or gravidity is a risk factor for coronary heart disease has been debated, but the question remains unresolved.

METHODS

We tested the association between the number of pregnancies and a variety of cardiovascular end points in two groups of women who had completed childbearing. One group comprised 2357 women who were followed for 28 years through the Framingham Heart Study, and the other 2533 women followed for at least 12 years through the first National Health and Nutrition Examination Survey National Epidemiologic Follow-up Study (NHEFS).

RESULTS

The rates of coronary heart disease were higher among multigravid women than among women who had never been pregnant, in both the Framingham Heart Study and the NHEFS, but in both studies, the higher rates were statistically significant only in women with six or more pregnancies. For the women in the Framingham Study, the rate ratio adjusted for age and educational level in the group with six or more pregnancies (as compared with women who had never been pregnant) was 1.6 (95 percent confidence interval, 1.1 to 2.2). For the women in the NHEFS, the same adjusted rate ratio was 1.5 (95 percent confidence interval, 1.1 to 1.9). Adjustments for other known cardiovascular risk factors, including weight, did not markedly alter this risk. The rate of total cardiovascular disease was also significantly higher among multigravid women in the Framingham Study than in the women who had never been pregnant.

CONCLUSIONS

In two prospective American studies, having six or more pregnancies was associated with a small but consistent increase in the risk of coronary heart disease and cardiovascular disease. Whether gravidity itself or some other unmeasured factor accounts for the increase in risk that we observed requires further investigation.

An epidemiologic study of non-occupational lifting as a risk factor for herniated lumbar intervertebral disc. The Northeast Collaborative Group on Low Back Pain

An epidemiologic case-control study of herniated lumbar intervertebral disc was conducted in Springfield, Massachusetts, New Brunswick, New Jersey, and New York, New York, to evaluate the role of several possible risk factors in the etiology of this disorder. Patients with signs and symptoms of herniated lumbar disc (N = 287) were matched to control subjects without back pain by age, sex, source of care, and geographic area. Of the total case-subject group, 177 were confirmed by surgery, computed tomographic scan, myelogram, or magnetic resonance imaging. This article focuses on non-occupational lifting, an activity not previously reported on. Frequent lifting of objects or children weighing 25 or more pounds with knees straight and back bent was associated with increased risk of herniated lumbar disc. This association was particularly strong among confirmed case subjects (relative risk = 3.95). Positive associations among confirmed case subjects were also seen for frequent lifting with arms extended (relative risk = 1.87) and twisting while lifting (relative risk = 1.90). No associations were found for frequent stretching or carrying. If confirmed in other investigations, these data suggest that instruction in lifting techniques should be extended into the home.

Exogenous calciferol (vitamin D) and vitamin D endocrine status among elderly nursing home residents in the New York City area

OBJECTIVE

To determine the role and relative importance of sources of exogenous calciferol (vitamin D) in maintaining vitamin D endocrine status in the mid-winter and early spring in a representative sample of institutionalized elderly persons in the New York City area.

DESIGN

Cross-sectional survey.

SETTING

A privately-run urban nursing home and the long-term care unit of a suburban public hospital.

PARTICIPANTS

Residents aged 60 years and older scheduled for a routine annual physical examination and an additional group of individuals ascertained by random sampling. Those with a history of anti-convulsant or glucocorticoid use, liver disease, chronic renal disease (or serum creatinine > 1.5 mg/dL), parathyroid disease, Paget's disease, gastric surgery, or pharmacological vitamin D use were excluded. Of 301 sampled individuals, 221 were found eligible to participate, and 109 were successfully enrolled.

RESULTS

The average vitamin D intake was 379 IU/day (range 55-1006 IU/day) and total vitamin D intake was below the Recommended Dietary Allowance in 16% of subjects. Fifty percent of total vitamin D intake came from fortified milk, and 26% came from vitamin supplements. Vitamin supplement use was not associated with low dietary intake. Among subjects taking a supplement containing 400 IU/day, none had serum calcidiol levels below 15 ng/mL, while among subjects with vitamin D intake between 200 and 400 IU/day, 46% had serum calcidiol levels below 15 ng/mL and 14% had calcidiol levels below 10 ng/mL. Vitamin D intake from non-supplement sources (but not from supplements) appeared to have a negative association with serum calcitriol levels.

CONCLUSIONS

Many nursing home residents may require vitamin supplements in order to achieve optimal levels of calciferol replacement. The choice of a vehicle for calciferol replacement may affect calcitriol levels.