PubMed Health⌕ Search

Biomedical subjects

David F Williamson

Publications and source records attributed to David F Williamson.

At least 19 recordsLinked to original sources
PubMed2007

Estimation of attributable number of deaths and standard errors from simple and complex sampled cohorts.

Estimates of the attributable number of deaths (AD) from all causes can be obtained by first estimating population attributable risk (AR) adjusted for confounding covariates, and then multiplying the AR by the number of deaths determined from vital mortality statistics that occurred in the population for a specific time period. Proportional hazard regression estimates of adjusted relative hazards obtained from mortality follow-up data from a cohort is combined with a joint distribution of risk factor and confounders to compute an adjusted AR. Two estimators of adjusted AR are examined. These estimators differ according to which reference population is used to obtain the joint distribution of risk factor and confounders. Two types of reference populations were considered: (i) the population represented by the baseline cohort and (ii) a population that is external to the cohort. Methods used in survey sampling are applied to obtain estimates of the variance of the AD estimator. These variances can be applied to data that range from simple random samples to multistage stratified cluster samples, which are used in national household surveys. The variance estimation of AD is illustrated in an analysis of excess deaths due to having a non-ideal body mass index using the second National Health and Examination Survey (NHANES) Mortality Study and the 1999-2002 NHANES. These methods can also be used to estimate the attributable number of cause-specific deaths and their standard errors when the time period for the accrual of deaths is short.

Cohort Studies↗
PubMed2006

The association between quality of care and the intensity of diabetes disease management programs.

BACKGROUND: Although disease management programs are widely implemented, little is known about their effectiveness. OBJECTIVE: To determine whether disease management by physician groups is associated with diabetes care processes, control of intermediate outcomes, or the amount of medication used when intermediate outcomes are above target levels. DESIGN: Cross-sectional study. SETTING: Patients were randomly sampled from 63 physician groups nested in 7 health plans sponsored by Translating Research into Action for Diabetes (87%) and from 4 health plans with individual physician contracts (13%). PATIENTS: 8661 adults with diabetes who completed a survey (2000-2001) and had medical record data. MEASUREMENTS: Physician group and health plan directors described their organizations' use of physician reminders, performance feedback, and structured care management on a survey; their responses were used to determine measures of intensity of disease management. The current study measured 8 processes of care, including most recent hemoglobin A1c level, systolic blood pressure, serum low-density lipoprotein cholesterol level, and several measures of medication use. RESULTS: Increased use of any of 3 disease management strategies was significantly associated with higher adjusted rates of retinal screening, nephropathy screening, foot examinations, and measurement of hemoglobin A1c levels. Serum lipid level testing and influenza vaccine administration were associated with greater use of structured care management and performance feedback. Greater use of performance feedback correlated with an increased rate of foot examinations (difference, 5 percentage points [95% CI, 1 to 8 percentage points]), and greater use of physician reminders was associated with an increased rate of nephropathy screening (difference, 15 percentage points [CI, 6 to 23 percentage points]). No strategies were associated with intermediate outcome levels or level of medication management. LIMITATIONS: Physician groups were not randomly sampled from population-based listings, and disease management strategies were not randomly allocated across groups. CONCLUSIONS: Disease management strategies were associated with better processes of diabetes care but not with improved intermediate outcomes or level of medication management. A greater focus on direct measurement, feedback, and reporting of intermediate outcome levels or of level of medication management may enhance the effectiveness of these programs.

Aged↗
PubMed2006

Correlates of health-related quality of life in overweight and obese adults with type 2 diabetes.

OBJECTIVE: This paper describes and examines conceptually relevant correlates of health-related quality of life (HRQL) in overweight or obese persons with type 2 diabetes. Research Design and Procedures: The investigation was a cross-sectional study of 5145 overweight or obese adults with type 2 diabetes between the ages of 45 and 74 years. Analyses examined the relationship that demographic characteristics, disease burden, and cardiovascular fitness had with HRQL: the Short Form 36 (SF-36) and the Beck Depression Inventory (BDI) II. RESULTS: Means for the SF-36 physical component summary (PCS) scores, the mental component summary scores, and the BDI-II were as follows: 47.0, 54.0, and 5.7. Less desirable PCS scores were related to several comorbidities, insulin use, physical complaints, a high BMI, low metabolic equivalent (MET) capacity, and lower education. Interactions between categories of obesity and MET capacity revealed that greater BMI was related to lower PCS scores when individuals had lower MET capacities yet was absent for those individuals who had higher MET capacities. In addition, although greater BMI was associated with more severe depressive symptomatology, this association was the most dramatic for those with class III obesity who had low MET capacity. DISCUSSION: Although participants in Look AHEAD had a favorable profile on the SF-36 and the BDI-II at baseline, lower PCS scores were related to disease severity and the presence of other comorbidities. More important, although the temporal ordering of associations cannot be determined in a cross-sectional design, the interactions between obesity class and MET capacity suggest that the adverse effect of BMI on PCS and BDI-II scores may be buffered by higher MET capacities.

Aged↗
PubMed2005

Excess deaths associated with underweight, overweight, and obesity.

CONTEXT: As the prevalence of obesity increases in the United States, concern over the association of body weight with excess mortality has also increased. OBJECTIVE: To estimate deaths associated with underweight (body mass index [BMI] <18.5), overweight (BMI 25 to <30), and obesity (BMI > or =30) in the United States in 2000. DESIGN, SETTING, AND PARTICIPANTS: We estimated relative risks of mortality associated with different levels of BMI (calculated as weight in kilograms divided by the square of height in meters) from the nationally representative National Health and Nutrition Examination Survey (NHANES) I (1971-1975) and NHANES II (1976-1980), with follow-up through 1992, and from NHANES III (1988-1994), with follow-up through 2000. These relative risks were applied to the distribution of BMI and other covariates from NHANES 1999-2002 to estimate attributable fractions and number of excess deaths, adjusted for confounding factors and for effect modification by age. MAIN OUTCOME MEASURES: Number of excess deaths in 2000 associated with given BMI levels. RESULTS: Relative to the normal weight category (BMI 18.5 to <25), obesity (BMI > or =30) was associated with 111,909 excess deaths (95% confidence interval [CI], 53,754-170,064) and underweight with 33,746 excess deaths (95% CI, 15,726-51,766). Overweight was not associated with excess mortality (-86,094 deaths; 95% CI, -161,223 to -10,966). The relative risks of mortality associated with obesity were lower in NHANES II and NHANES III than in NHANES I. CONCLUSIONS: Underweight and obesity, particularly higher levels of obesity, were associated with increased mortality relative to the normal weight category. The impact of obesity on mortality may have decreased over time, perhaps because of improvements in public health and medical care. These findings are consistent with the increases in life expectancy in the United States and the declining mortality rates from ischemic heart disease.

Adult↗
PubMed2005

Secular trends in cardiovascular disease risk factors according to body mass index in US adults.

CONTEXT: Prevalence of obesity in the United States has increased dramatically in recent decades, but the magnitude of change in cardiovascular disease (CVD) risk factors among the growing proportion of overweight and obese Americans remains unknown. OBJECTIVE: To examine 40-year trends in CVD risk factors by body mass index (BMI) groups among US adults aged 20 to 74 years. DESIGN, SETTING, AND PARTICIPANTS: Analysis of 5 cross-sectional, nationally representative surveys: National Health Examination Survey (1960-1962); National Health and Nutrition Examination Survey (NHANES) I (1971-1975), II (1976-1980), and III (1988-1994); and NHANES 1999-2000. MAIN OUTCOME MEASURES: Prevalence of high cholesterol level (> or =240 mg/dL [> or =6.2 mmol/L] regardless of treatment), high blood pressure (> or =140/90 mm Hg regardless of treatment), current smoking, and total diabetes (diagnosed and undiagnosed combined) according to BMI group (lean, <25; overweight, 25-29; and obese, > or =30). RESULTS: The prevalence of all risk factors except diabetes decreased over time across all BMI groups, with the greatest reductions observed among overweight and obese groups. Compared with obese persons in 1960-1962, obese persons in 1999-2000 had a 21-percentage-point lower prevalence of high cholesterol level (39% in 1960-1962 vs 18% in 1999-2000), an 18-percentage-point lower prevalence of high blood pressure (from 42% to 24%), and a 12-percentage-point lower smoking prevalence (from 32% to 20%). Survey x BMI group interaction terms indicated that compared with the first survey, the prevalence of high cholesterol in the fifth survey had fallen more in obese and overweight persons than in lean persons (P<.05). Survey x BMI changes in blood pressure and smoking were not statistically significant. Changes in risk factors were accompanied by increases in lipid-lowering and antihypertensive medication use, particularly among obese persons. Total diabetes prevalence was stable within BMI groups over time, as nonsignificant 1- to 2-percentage-point increases occurred between 1976-1980 and 1999-2000. CONCLUSIONS: Except for diabetes, CVD risk factors have declined considerably over the past 40 years in all BMI groups. Although obese persons still have higher risk factor levels than lean persons, the levels of these risk factors are much lower than in previous decades.

Adult↗
PubMed2005

A structured review of randomized controlled trials of weight loss showed little improvement in health-related quality of life.

OBJECTIVE: To estimate the effect of weight-loss interventions on health-related quality of life (HrQoL) in randomized controlled trials (RCTs); to conduct a meta-analysis of weight-loss treatment on depressive symptoms; and, to examine methodological and presentation issues that compromise study validity. STUDY DESIGN AND SETTING: We conducted a structured review of 34 RCTs with weight-loss interventions that reported the relationship between HrQoL and treatment at two or more time points. We also evaluated study quality. RESULTS: Trials lasted 6 weeks to 208 weeks and evaluated behavioral, surgical, or pharmacologic interventions. Nine of 34 trials showed HrQoL improvements in generic measures. Obesity-specific measures were more likely to show improvement in response to treatment than non-obesity-specific measures. Meta-analysis showed no treatment effect on depressive symptoms. Most trials tracked loss to follow-up and conducted intent-to-treat analysis, but only four trials concealed recruitment staff to randomization and 14 blinded the investigation team to randomization. CONCLUSION: HrQoL outcomes, including depression, were not consistently improved in RCTs of weight loss. The overall quality of these clinical trials was poor. Better-designed RCTs using standardized HrQoL measures are needed to determine the extent to which weight loss improves HrQoL.

Adult↗
PubMed2005

Childhood residential mobility and multiple health risks during adolescence and adulthood: the hidden role of adverse childhood experiences.

BACKGROUND: Throughout US history, US society has been characterized by its high degree of residential mobility. Previous data suggest a relationship between mobility and increased health risk, but this relationship might be confounded by unmeasured adverse childhood experiences (ACEs). OBJECTIVES: To examine the relationship of childhood residential mobility to health problems during adolescence and adulthood and to determine how much these apparent relationships may result from underlying ACEs. DESIGN, SETTING, AND PARTICIPANTS: Retrospective cohort study of 8116 adults who completed a survey that included childhood residential mobility, ACEs (childhood abuse, childhood neglect, and household dysfunction), and multiple health problems. MAIN OUTCOME MEASURES: Number of childhood residential moves and number of ACEs (ACE score) were assessed for relationships to depressed affect, attempted suicide, alcoholism, smoking, early sexual initiation, and teenaged pregnancy. RESULTS: After adjustment for demographic variables, the risk of high residential mobility during childhood (> or = 8 moves) was 1.7- to 3.1-fold for each ACE, and increased with the number of ACEs. Compared with respondents who never moved, the odds of health risk for respondents with high mobility during childhood ranged from 1.3 (for smoking) to 2.5 (for suicide). However, when the number of ACEs was entered into multivariate models, the relationship between mobility and health problems was greatly reduced. CONCLUSIONS: Adverse childhood experiences are strongly associated with frequent residential mobility. Moreover, the apparent relationship between childhood mobility and various health risks is largely explained by ACEs. Thus, previous studies showing a relationship between residential mobility and negative outcomes were likely confounded by unmeasured ACEs.

Adolescent↗
PubMed2005

Combination pharmacotherapy for cardiovascular disease prevention: threat or opportunity for public health?

In a series of three papers in the British Medical Journal (June 28, 2003), Wald et al. proposed that the Polypill can reduce the incidence of coronary heart disease by 88%, and stroke by 80%, if taken by all people aged > or = 55, as well as people of any age with existing cardiovascular disease or diabetes. We review the rationale and uniqueness behind this idea, identify the concerns and questions that need to be addressed, discuss whether this strategy is a threat or an opportunity for public health, and hope that this will stimulate further debate.

Cardiovascular Diseases↗
PubMed2004

Methods of calculating deaths attributable to obesity.

Previously reported estimates of deaths attributable to obesity in the United States have been based on a method that only partially adjusts for confounding and does not allow for effect modification. In this study, the authors investigated the possible magnitude and direction of bias in estimating deaths attributable to obesity when such a method is used. Hypothetical examples are based on 1991 US population data and published relative risks. Incomplete adjustment for confounding of the obesity-mortality relation by age and sex led to a 17% overestimation of deaths due to obesity. Additional bias resulted from slight differences between the derivation cohort and the target population. For example, a difference of three percentage points in the proportion of people 80 years of age or older led to a 42% overestimation of deaths due to obesity. In addition, these estimates appear to be sensitive to minor differences in relative risks between a derivation cohort and the target population. A difference of 0.20 in relative risks almost doubled the number of deaths (97% overestimation). Estimates of deaths attributable to obesity can be biased if confounding and effect modification are not properly taken into account or if the relative risks are not estimated accurately.

Adolescent↗
PubMed2004

Primary prevention of type 2 diabetes mellitus by lifestyle intervention: implications for health policy.

More than 18 million Americans currently have diabetes mellitus. The economic and human cost of the disease is devastating. In the United States, diabetes is the most common cause of blindness among working-age adults, the most common cause of nontraumatic amputations and end-stage renal disease, and the sixth most common cause of death. For the cohort of Americans born in 2000, the estimated lifetime risk for diabetes is more than 1 in 3. In the next 50 years, the number of diagnosed cases of diabetes is predicted to increase by 165% in the United States, with the largest relative increases seen among African Americans, American Indians, Alaska Natives, Asian and Pacific Islanders, and Hispanic/Latino persons. Compelling scientific evidence indicates that lifestyle change prevents or delays the occurrence of type 2 diabetes in high-risk groups. This body of evidence from randomized, controlled trials conducted in 3 countries has definitively established that maintenance of modest weight loss through diet and physical activity reduces the incidence of type 2 diabetes in high-risk persons by about 40% to 60% over 3 to 4 years. The number of persons at high risk for type 2 diabetes is similar to the number of persons who have diabetes. This paper summarizes scientific evidence supporting lifestyle intervention to prevent type 2 diabetes and discusses major policy challenges to broad implementation of lifestyle intervention in the health system.

Behavior Therapy↗
PubMed2004

The interrelatedness of multiple forms of childhood abuse, neglect, and household dysfunction.

OBJECTIVE: Childhood abuse and other adverse childhood experiences (ACEs) have historically been studied individually, and relatively little is known about the co-occurrence of these events. The purpose of this study is to examine the degree to which ACEs co-occur as well as the nature of their co-occurrence. METHOD: We used data from 8,629 adult members of a health plan who completed a survey about 10 ACEs which included: childhood abuse (emotional, physical, and sexual), neglect (emotional and physical), witnessing domestic violence, parental marital discord, and living with substance abusing, mentally ill, or criminal household members. The bivariate relationship between each of these 10 ACEs was assessed, and multivariate linear regression models were used to describe the interrelatedness of ACEs after adjusting for demographic factors. RESULTS: Two-thirds of participants reported at least one ACE; 81%-98% of respondents who had experienced one ACE reported at least one additional ACE (median: 87%). The presence of one ACE significantly increased the prevalence of having additional ACEs, elevating the adjusted odds by 2 to 17.7 times (median: 2.8). The observed number of respondents with high ACE scores was notably higher than the expected number under the assumption of independence of ACEs (p <.0001), confirming the statistical interrelatedness of ACEs. CONCLUSIONS: The study provides strong evidence that ACEs are interrelated rather than occurring independently. Therefore, collecting information about exposure to other ACEs is advisable for studies that focus on the consequences of a specific ACE. Assessment of multiple ACEs allows for the potential assessment of a graded relationship between these childhood exposures and health and social outcomes.

California↗
PubMed2004

Weight cycling and the risk of developing type 2 diabetes among adult women in the United States.

OBJECTIVE: To assess the role of weight cycling independent of BMI and weight change in predicting the risk of developing type 2 diabetes. RESEARCH METHODS AND PROCEDURES: A six-year follow-up of 46,634 young and middle-aged women in the Nurses' Health Study II was conducted. Women who had intentionally lost > or = 20 lbs at least three times between 1989 and 1993 were classified as severe weight cyclers. Women who had intentionally lost > or = 10 lbs at least three times were classified as mild weight cyclers. The outcome was physician-diagnosed type 2 diabetes. RESULTS: Between 1989 and 1993, approximately 20% of the women were mild weight cyclers, and 1.6% were severe weight cyclers. BMI in 1993 was positively associated with weight-cycling status (p < 0.001). During 6 years of follow-up (1993 to 1999), 418 incident cases of type 2 diabetes were documented. BMI in 1993 had a strong association with the risk of developing diabetes. Compared with women with a BMI between 17 and 22 kg/m(2), those with a BMI between 25 and 29.9 kg/m(2) were approximately seven times more likely to develop diabetes, and those with a BMI > or = 35 kg/m(2) were 63 times more likely to be diagnosed with type 2 diabetes. After adjustment for BMI, neither mild (relative risk = 1.11, 95% confidence interval, 0.89 to 1.37) nor severe (relative risk = 1.39, 95% confidence interval, 0.90 to 2.13) weight cycling predicted risk of diabetes. DISCUSSION: Weight cycling was strongly associated with BMI, but it was not independently predictive of developing type 2 diabetes.

Adult↗
PubMed2004

Estimating deaths attributable to obesity in the United States.

Estimates of deaths attributable to obesity in the United States rely on estimates from epidemiological cohorts of the relative risk of mortality associated with obesity. However, these relative risk estimates are not necessarily appropriate for the total US population, in part because of exclusions to control for baseline health status and exclusion or underrepresentation of older adults. Most deaths occur among older adults; estimates of deaths attributable to obesity can vary widely depending on the assumptions about the relative risks of mortality associated with obesity among the elderly. Thus, it may be difficult to estimate deaths attributable to obesity with adequate accuracy and precision. We urge efforts to improve the data and methods for estimating this statistic.

Adult↗