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Biomedical subjects

D F Williamson

Publications and source records attributed to D F Williamson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Weight cycling, weight gain, and risk of hypertension in women.

To assess prospectively the relation between body mass index, weight gain, repeated intentional weight losses, and the risk of self-reported hypertension, the authors studied 46,224 women who were participants in the Nurses Health Study II, who were free of hypertension in 1993, and who completed questions on intentional weight losses between 1989 and 1993. Women who reported they had intentionally lost > or =20 lbs (9 kg) > or =3 times were classified as severe weight cyclers. Women who had intentionally lost > or =10 lbs (4.5 kg) > or =3 times, but who did not meet the criteria for severe weight cycling, were classified as mild weight cyclers. Between 1993 and 1995, 1,107 incident cases of diagnosed hypertension were reported. Body mass index and weight gain, but not weight cycler status, were independently associated with the development of hypertension. For each 10 lb (4.5 kg) gain in weight between 1989 and 1993, the risk of hypertension increased 20% (odds ratio (OR) = 1.20, 95% confidence interval (CI) 1.15, 1.24). After adjustment for body mass index and weight gain, the risks associated with mild weight cycling (OR = 1.15, 95% CI 1.00, 1.33) and severe weight cycling (OR = 1.13, 95% CI 0.79, 1.61) were small and not significant. Thus, the results of this study offer support for the current weight guidelines and provide further evidence of the health risks associated with excessive weight and weight gain. However, these data do not suggest an independent effect of weight cycling on risk of hypertension.

Adult↗
PubMed1999

Consequences of the use of different measures of effect to determine the impact of age on the association between obesity and mortality.

The impact of using different measures of the effect of obesity on mortality across age groups has not been explored. The authors examined this issue by using mortality data from 62,116 men and 262,965 women in the Cancer Prevention Study-I (1960-1972). Measures of effect were calculated separately, by decade of age, for five groups of participants aged 30-79 years. The rate ratio associated with obesity declined with age, from 2.60 (men) and 1.99 (women) for participants aged 30-39 years to 1.24 (men) and 1.15 (women) for those aged 70-79 years. In contrast, the rate differences between obese and reference-weight participants increased with age, from 201 (men) and 112 (women) deaths per 100,000 person-years for those in the youngest decade to 1,379 (men) and 626 (women) deaths per 100,000 person-years for those in the oldest decade. The years of life lost attributable to obesity tended to increase with age but declined for those in the oldest decade. The rate advancement period declined with decade of age. Standardization of estimates to a population changed some age-associated trends. The direction of trends varied regarding the effect of obesity on mortality across age groups, depending on the measure of effect used.

Adult↗
PubMed1999

Long-term weight patterns and risk for cholecystectomy in women.

BACKGROUND: Obesity and rapid weight loss in obese persons are known risk factors for gallstones. However, the effect of intentional, long-term, moderate weight changes on the risk for gallstones is unclear. OBJECTIVE: To study long-term weight patterns in a cohort of women and to examine the relation between weight pattern and risk for cholecystectomy. DESIGN: Prospective cohort study. SETTING: 11 U.S. states. PARTICIPANTS: 47,153 female registered nurses who did not undergo cholecystectomy before 1988. MEASUREMENTS: Cholecystectomy between 1988 and 1994 (ascertained by patient self-report). RESULTS: During the exposure period (1972 to 1988), there was evidence of substantial variation in weight due to intentional weight loss during adulthood. Among cohort patients, 54.9% reported weight cycling with at least one episode of intentional weight loss associated with regain. Of the total cohort, 20.1% were light cyclers (5 to 9 lb of weight loss and gain), 18.8% were moderate cyclers (10 to 19 lb of weight loss and gain), and 16.0% were severe cyclers (> or = 20 lb of weight loss and gain). Net weight gain without cycling occurred in 29.3% of women; net weight loss without cycling was the least common pattern (4.6%). Only 11.1% of the cohort maintained weight within 5 lb over the 16-year period. In the study, 1751 women had undergone cholecystectomy between 1988 and 1994. Compared with weight maintainers, the relative risk for cholecystectomy (adjusted for body mass index, age, alcohol intake, fat intake, and smoking) was 1.20 (95% CI, 0.96 to 1.50) among light cyclers, 1.31 among moderate cyclers (CI, 1.05 to 1.64), and 1.68 among severe cyclers (CI, 1.34 to 2.10). CONCLUSION: Weight cycling was highly prevalent in this large cohort of middle-aged women. The risk for cholecystectomy associated with weight cycling was substantial, independent of attained relative body weight.

Adult↗
PubMed1999

Prospective study of intentional weight loss and mortality in overweight white men aged 40-64 years.

Although 25% of US men indicate that they are trying to lose weight, the association between intentional weight loss and longevity in men is unknown. The authors analyzed prospective data from 49,337 overweight (initial body mass index > or =27) white men aged 40-64 years who, in 1959-1960, answered questions on weight change direction, amount, time interval, and intent. Vital status was determined in 1972. Proportional hazards regression estimated mortality rate ratios for men who intentionally lost weight compared with men with no weight change. Analyses were stratified by health status and adjusted for age, initial body mass index, smoking status, alcohol intake, education, physical activity, health history, and physical symptoms. Among men with no reported health conditions (n = 36,280), intentional weight loss was not associated with total, cardiovascular (CVD), or cancer mortality, but diabetes-associated mortality was increased 48% (95% confidence interval (CI) -7% to +133%) among those who lost 20 pounds (9.1 kg) or more; this increase was largely related to non-CVD mortality. Among men with reported health conditions (n = 13,057), intentional weight loss had no association with total or CVD mortality, but cancer mortality increased 25% (95% confidence interval -4% to +63%) among those who lost 20 pounds or more. Diabetes-associated mortality was reduced 32% (95% confidence interval -52% to -5%) among those who lost less than 20 pounds and 36% (95% confidence interval -49% to -20%) among those who lost more than 20 pounds. These results and those from our earlier study in women (Williamson et al., Am J Epidemiol 1995;141:1128-41) suggest that intentional weight loss may reduce the risk of dying from diabetes, but not from CVD. In observational studies, however, it is difficult to separate intentional weight loss from unintentional weight loss due to undiagnosed, underlying disease. Well-designed observational studies, as well as randomized controlled trials, are needed to determine whether intentional weight loss reduces CVD mortality.

Adult↗
PubMed1999

Prospective study of intentionality of weight loss and mortality in older women: the Iowa Women's Health Study.

Several epidemiologic investigations have suggested that weight loss is associated with increased mortality risk but have not examined whether the weight loss was intentional or unintentional. The authors examined whether the association between weight loss and mortality differs by whether the weight loss was intentional or unintentional as part of the Iowa Women's Health Study, a prospective cohort study of health risk factors in postmenopausal women. Women aged 55-69 years completed questions about intentional and unintentional weight losses since age 18 years via mail survey in 1992 and were followed through 1995. One or more intentional weight loss episodes of 20 or more pounds (> or =9.1 kg) during adulthood was not significantly associated with higher total or cardiovascular disease mortality risk compared with never losing > or =20 pounds. One or more unintentional weight loss episodes of 20 or more pounds was associated with a 26-57% higher total mortality risk and a 51-114% higher cardiovascular disease mortality risk, compared with never losing 20 or more pounds. Associations between unintentional weight loss and increased mortality risk were confined mostly to women with prevalent disease, hypertension, or diabetes. Patterns of association did not vary by overweight status. These findings suggest that the association between weight loss and increased mortality risk observed in epidemiologic studies may be due to unintentional weight loss that reflects existing disease and not due to intentional weight loss.

Aged↗
PubMed1999

Meta-analysis of the effect of excluding early deaths on the estimated relationship between body mass index and mortality.

OBJECTIVES: Prospective cohort studies typically observe U- or J-shaped relationships between body mass index (BMI) (kg/m2) and mortality. However, some studies suggest that the elevated mortality at lower BMIs is due to confounding by pre-existing occult disease and recommend eliminating subjects who die during the first several (k) years of follow-up. This meta-analysis tests the effects of such early death exclusion on the BMI-mortality association. RESEARCH METHODS AND PROCEDURES: Studies identified from MEDLINE, review articles, ancestry analyses, and the "invisible college." INCLUDED STUDIES: 1) measured relative body weight at baseline; 2) included at least 1000 subjects; 3) reported results with and without early-death exclusion, or relevant data; and 4) did not study exclusively diseased populations. Blank tables were mailed to 131 investigators covering 59 databases. Completed tables (n = 16 databases), electronic raw data (n = 7 databases), and original articles (n = 6 databases) provided final data. Meta-analytic regressions compared the BMI-mortality association with and without early death exclusion. The sample included 29 studies and 1,954,345 subjects. RESULTS: The effect of eliminating early deaths was statistically significant but minuscule in magnitude. Implementation of early death exclusion was estimated to shift the BMI associated with minimum mortality only 0.4 units for men and 0.6 units for women at age 50. Even at a BMI 16, the estimated relative risk (compared to BMI 25) decreased only 0.008 units for men and 0.076 units for women at age 50. DISCUSSION: Results indicate that either pre-existing disease does not confound the BMI-mortality association or eliminating early deaths is inefficient for reducing that confounding.

Adolescent↗
PubMed1999

The public health epidemiology of type 2 diabetes in children and adolescents: a case study of American Indian adolescents in the Southwestern United States.

Type 2 diabetes among children and adolescents is a newly recognized disease in the United States. Because obesity and physical inactivity are increasing in children and adolescents, the prevalence of pediatric type 2 diabetes may increase and eventually become an important cause of adult morbidity and mortality. Data on type 2 diabetes in adolescents aged 15-19 years were compared between two sources: systematic population screening of the Gila River Indian Community by the National Institutes of Health (NIH), and reported cases by the Indian Health Service (IHS) from clinics in the Southwestern US. The current NIH estimate of prevalence of type 2 diabetes was much higher than the IHS estimate (5.1% vs. 0.46%). Both data sources, however, suggest a secular increase in prevalence between 1986 and 1996-97. These data are used to discuss the principles, applications, and challenges for accurate epidemiologic assessment of type 2 diabetes in children and adolescents.

Adolescent↗
PubMed1999

High prevalence of impaired fasting glucose and type 2 diabetes mellitus in Penghu Islets, Taiwan: evidence of a rapidly emerging epidemic?

The purpose of this study was to estimate the prevalence of type 2 diabetes and impaired fasting glucose (IFG) in Penghu, Taiwan and compare these estimates with those of the US (NHANES III). Diabetes and IFG (American Diabetes Association criteria, 1997) were assessed among a stratified random sample of 2500 residents of Penghu Islands, Taiwan. The prevalence (age-adjusted to world adult population) of diabetes and IFG were 16.8% (95% CI 15.0-18.6) and 21.0% (95% CI 19.0-23.0), respectively, among Penghu Islanders in Taiwan. Age sex-specific diabetes prevalence ranged from 10.0% in men aged 40-49 years to 29.4% in women aged 60-69 years. Prevalence of IFG ranged from 14.7% in women aged 40-49 years to 30.7% in men aged 50-59 years. Age, body mass index (BMI), and family history of diabetes were each independently associated with both diabetes and IFG. In addition, female gender, apolipoprotein B and triglyceride concentrations were associated with diabetes, and hypertension and apolipoprotein B concentration with IFG. Among persons > or = 40 years in Penghu, Taiwan, the prevalence of diabetes is up to a third higher and the prevalence of IFG is up to three times higher than comparably aged Americans, despite their having a mean BMI 2.2-3.2 kg/m2 lower than Americans. The alarmingly high prevalence of IFG in Taiwan may indicate an emerging diabetes epidemic.

Adult↗
PubMed1999

Simulation study of the effects of excluding early deaths on risk factor-mortality analyses in the presence of confounding due to occult disease: the example of body mass index.

PURPOSE: Estimating the effects of continuous chronic disease risk factors on mortality is an area that generates confusion and controversy. The frequently observed U-shaped or J-shaped relationships between the risk factors and mortality are often in contrast with presumed monotone relationships. Therefore, some investigators suggest that subjects dying during the first k years of follow-up (where k is some positive number less than the total length of follow-up) be excluded from statistical analyses. The rationale for this approach is that subjects dying during the first k years of follow-up are likely to have some pre-existing occult disease that confounds the relationship between the risk factors and mortality. Excluding such subjects purportedly reduces bias due to this confounding. The purpose of this study was to test the effects of excluding subjects who die during the first k years of follow-up on the reduction of bias under a variety of situations. METHODS: Using body mass index (BMI; kg/m2) as an example, we conducted Monte Carlo simulations to investigate such effects. RESULTS: Results suggest that under the conditions investigated, the method of excluding early deaths does not reliably or substantially reduce bias due to confounding introduced by occult disease. CONCLUSION: Excluding subjects dying during the first k years of follow-up may not be a judicious strategy for handling confounding due to occult disease. Investigators are encouraged to develop alternative methods.

Bias↗
PubMed1999

The use of population attributable risk to estimate the impact of prevention and early detection of type 2 diabetes on population-wide mortality risk in US males.

The Population Attributable Risk (PAR) represents the proportion of the deaths (in a specified time) in the whole population that may be preventable if a cause of mortality were totally eliminated. This population-based measure was used to assess the potential impact of three public health interventions for type 2 diabetes (early detection + standard therapy; early detection + intensive therapy; and primary prevention) on the mortality risk from all causes and from cardiovascular (CVD) diseases. Potential reduction in mortality risks for several levels of compliance or implementation (25%, 50%, 75%, 100%) for each intervention were also estimated. Results suggest that among males aged 45-74 years, the interventions may have greater population-wide impact on total deaths among black males, and greater impact on the CVD deaths among white males. Overall, primary prevention (reduction in all-cause mortality 6.2-10.0%, and CVD mortality 7.9-9.0%) may offer greater marginal benefit than screening and early treatment (reduction in all-cause mortality 3.5-8.3%, and CVD mortality 2.8-8.6%). Often the question facing policy makers is not simply whether to but how much of an intervention is worth implementing? Estimated benefits for various intensities of intervention (as provided) may be useful to assess the likely marginal benefits of each intervention, and can be especially useful if combined with estimated marginal costs.

Black or African American↗
PubMed1999

Dose-effect of fenfluramine use on the severity of valvular heart disease among fen-phen patients with valvulopathy.

OBJECTIVE: To determine whether the severity of valvulopathy was associated with the dosage of fenfluramine taken by fenfluramine-phentermine users with valvulopathy. DESIGN: Out of 105 suspected valvulopathy case reports received by the US Food and Drug Administration (FDA) among fenfluramine-phentermine users, 74 patients meeting FDA case definition for valvulopathy were included in this study. Patients with severe valvulopathy were classified as those either undergoing valve replacement surgery or having severe aortic or mitral regurgitation; all other patients were considered to have less severe valvulopathy. RESULTS: The proportion with severe valvulopathy increased from 20-66% with increasing fenfluramine dosage from </=40 mg/d to >/=60 mg/d. Compared with patients taking<40 mg/d fenfluramine, patients taking >/=60 mg/d had an adjusted odds ratio of 9.2 (95% confidence interval=2.1-40.8) for severe valvulopathy. CONCLUSION: Compared to patients with less severe valvulopathy, those with severe valvulopathy were substantially more likely to have taken >/=60 mg/d fenfluramine.

Adult↗
PubMed1999

Report of a National Institutes of Health--Centers for Disease Control and Prevention workshop on the feasibility of conducting a randomized clinical trial to estimate the long-term health effects of intentional weight loss in obese persons.

A workshop was convened in 1997 by the National Institutes of Health and the Centers for Disease Control and Prevention to consider the need for and feasibility of conducting a randomized clinical trial to estimate the long-term health effects of intentional weight loss in obese persons. Although the benefits of weight loss in obese individuals may seem obvious, little information is available showing that intentional weight loss improves long-term health outcomes. Observational studies may be unable to provide convincing answers about the magnitude and direction of the health effects of intentional weight loss. Workshop participants agreed that a well-designed randomized clinical trial could answer several questions necessary for developing a rational clinical and public health policy for treating obesity. Such information will ultimately provide needed guidance on the risks and benefits of weight loss to health care providers and payers, as well as to millions of obese Americans.

Animals↗
PubMed1998

The effect of age on the association between body-mass index and mortality.

BACKGROUND: The effect of age on optimal body weight is controversial, and few studies have had adequate numbers of subjects to analyze mortality as a function of body-mass index across age groups. METHODS: We studied mortality over 12 years among white men and women who participated in the American Cancer Society's Cancer Prevention Study I (from 1960 through 1972). The 62,116 men and 262,019 women included in this analysis had never smoked cigarettes, had no history of heart disease, stroke, or cancer (other than skin cancer) at base line in 1959-1960, and had no history of recent unintentional weight loss. The date and cause of death for subjects who died were determined from death certificates. The associations between body-mass index (defined as the weight in kilograms divided by the square of the height in meters) and mortality were examined for six age groups in analyses in which we adjusted for age, educational level, physical activity, and alcohol consumption. RESULTS: Greater body-mass index was associated with higher mortality from all causes and from cardiovascular disease in men and women up to 75 years of age. However, the relative risk associated with greater body-mass index declined with age. For example, for mortality from cardiovascular disease, the relative risk associated with an increment of 1 in the body-mass index was 1.10 (95 percent confidence interval, 1.04 to 1.16) for 30-to-44-year-old men and 1.03 (95 percent confidence interval, 1.02 to 1.05) for 65-to-74-year-old men. For women, the corresponding relative risk estimates were 1.08 (95 percent confidence interval, 1.05 to 1.11) and 1.02 (95 percent confidence interval, 1.02 to 1.03). CONCLUSIONS: Excess body weight increases the risk of death from any cause and from cardiovascular disease in adults between 30 and 74 years of age. The relative risk associated with greater body weight is higher among younger subjects.

Adult↗