Alyson J. Littman

Association between Physical Performance and All-Cause Mortality in CKD

In older adults, measurements of physical performance assess physical function and associate with mortality and disability. Muscle wasting and diminished physical performance often accompany CKD, resembling physiologic aging, but whether physical performance associates with clinical outcome in CKD is unknown. We evaluated 385 ambulatory, stroke-free participants with stage 2-4 CKD enrolled in clinic-based cohorts at the University of Washington and University of Maryland and Veterans Affairs Maryland Healthcare systems. We compared handgrip strength, usual gait speed, timed up and go (TUAG), and 6-minute walking distance with normative values and constructed Cox proportional hazards models and receiver operating characteristic curves to test associations with all-cause mortality. Mean age was 61 years and the mean estimated GFR was 41 ml/min per 1.73 m(2). Measures of lower extremity performance were at least 30% lower than predicted, but handgrip strength was relatively preserved. Fifty deaths occurred during the median 3-year follow-up period. After adjustment, each 0.1-m/s decrement in gait speed associated with a 26% higher risk for death, and each 1-second longer TUAG associated with an 8% higher risk for death. On the basis of the receiver operating characteristic analysis, gait speed and TUAG more strongly predicted 3-year mortality than kidney function or commonly measured serum biomarkers. Adding gait speed to a model that included estimated GFR significantly improved the prediction of 3-year mortality. In summary, impaired physical performance of the lower extremities is common in CKD and strongly associates with all-cause mortality.

Reliability and validity of 2 single-item measures of psychosocial stress

Background: Practical limitations in epidemiologic research may necessitate use of only a few questions for assessing the complex phenomenon called “stress.” The objective of this study was to evaluate the measurement characteristics of 2 single-item measures on the amount of stress and the ability to handle stress. Methods: We selected 218 adults age 50 to 76 years living in western Washington state from a large prospective cohort study of lifestyle factors and cancer risk to evaluate the 3-month test–retest reliability and intermethod reliability of the stress questions. To assess the latter, we compared 2 single-item measures on stress with 3 more fully validated multi-item instruments on perceived stress, daily hassles, and life events, which assessed the same underlying constructs as the single-item measures. Results: The test–retest reliabilities for the single-item stress measures were good (kappa and intraclass correlations between 0.66 and 0.74). The intermethod reliabilities comparing the 2 single-item stress measures with 3 multi-item instruments were moderate (r = 0.31–0.46) and comparable to correlations observed among the 3 multi-item instruments (r = 0.25–0.47). Conclusions: The 2 single-item stress measures are reliable at measuring stress with validity similar to longer questionnaires. Single-item measures offer a practical instrument for assessing stress in large prospective epidemiologic studies that lack space for longer instruments.

Obesity and COPD: associated symptoms, health-related quality of life, and medication use.

Background: There is little data about the combined effects of COPD and obesity. We compared dyspnea, health-related quality of life (HRQoL), exacerbations, and inhaled medication use among patients who are overweight and obese to those of normal weight with COPD. Methods: We performed secondary data analysis on 364 Veterans with COPD. We categorized subjects by body mass index (BMI). We assessed dyspnea using the Medical Research Council (MRC) dyspnea scale and HRQoL using the St. Georges Respiratory Questionnaire. We identified treatment for an exacerbation and inhaled medication use in the past year. We used multiple logistic and linear regression models as appropriate, with adjustment for age, COPD severity, smoking status, and co-morbidities. Results: The majority of our population was male (n = 355, 98%) and either overweight (n = 115, 32%) or obese (n = 138, 38%). Obese and overweight subjects had better lung function (obese: mean FEV1 55.4% ±19.9% predicted, overweight: mean FEV1 50.0% ±20.4% predicted) than normal weight subjects (mean FEV1 44.2% ±19.4% predicted), yet obese subjects reported increased dyspnea [adjusted OR of MRC score ≥2 = 4.91 (95% CI 1.80, 13.39], poorer HRQoL, and were prescribed more inhaled medications than normal weight subjects. There was no difference in any outcome between overweight and normal weight patients. Conclusions: Despite having less severe lung disease, obese patients reported increased dyspnea and poorer HRQoL than normal weight patients. The greater number of inhaled medications prescribed for obese patients may represent overuse. Obese patients with COPD likely need alternative strategies for symptom control in addition to those currently recommended.

Dietary supplement use and medical conditions

BACKGROUND Over half of U.S. adults use vitamin or mineral supplements, and some are likely using supplements to treat chronic diseases or risk factors for disease. Information on the relationship between supplement use and medical conditions is useful to health professionals to understand the self-medication behavior of their patients, and important for researchers because medical conditions may be potential confounding factors in observational studies of supplement use and disease risk. METHODS The cross-sectional data in this report are from 45,748 participants, aged 50 to 75 years, who completed a self-administered, mailed questionnaire on current dietary supplement use (multivitamins plus 16 individual vitamins or minerals), medical history (cancer, cardiovascular-related diseases, and other self-reported medical conditions), and demographic characteristics. RESULTS Supplement use (mean number used at least once a week) was higher among respondents who were older, female, highly educated, Caucasian, and of normal body mass index (all p<0.001). After controlling for these covariates, supplement use was higher among those with the condition for 13 of the 21 conditions examined (p<0.01); only having diabetes or high stress was associated with using fewer supplements. For specific supplements, the strongest associations were for cardiovascular disease and its risk factors with vitamin E, niacin, and folate, and for calcium with indigestion and acid reflux disease. For several conditions, the relative odds of using specific supplements were consistently higher for men than for women. CONCLUSIONS Supplement use was associated with many medical conditions in this cohort. However, these cross-sectional data do not permit inferences about the temporal sequence. Some associations appeared to be based on evidence for efficacy (e.g., folate with coronary artery disease), and others could be based on misinformation (e.g., selenium with benign prostatic hyperplasia).

Long-term Use of β-Carotene, Retinol, Lycopene, and Lutein Supplements and Lung Cancer Risk: Results From the VITamins And Lifestyle (VITAL) Study

High-dose beta-carotene supplementation in high-risk persons has been linked to increased lung cancer risk in clinical trials; whether effects are similar in the general population is unclear. The authors examined associations of supplemental beta-carotene, retinol, vitamin A, lutein, and lycopene with lung cancer risk among participants, aged 50-76 years, in the VITamins And Lifestyle (VITAL) cohort Study in Washington State. In 2000-2002, eligible persons (n = 77,126) completed a 24-page baseline questionnaire, including detailed questions about supplement use (duration, frequency, dose) during the previous 10 years from multivitamins and individual supplements/mixtures. Incident lung cancers (n = 521) through December 2005 were identified by linkage to the Surveillance, Epidemiology, and End Results cancer registry. Longer duration of use of individual beta-carotene, retinol, and lutein supplements (but not total 10-year average dose) was associated with statistically significantly elevated risk of total lung cancer and histologic cell types; for example, hazard ratio = 2.02, 95% confidence interval: 1.28, 3.17 for individual supplemental lutein with total lung cancer and hazard ratio = 3.22, 95% confidence interval: 1.29, 8.07 for individual beta-carotene with small-cell lung cancer for >4 years versus no use. There was little evidence for effect modification by gender or smoking status. Long-term use of individual beta-carotene, retinol, and lutein supplements should not be recommended for lung cancer prevention, particularly among smokers.

Chlamydia pneumoniae and Lung Cancer: Epidemiologic Evidence

Chlamydia pneumoniae is a common cause of acute respiratory infection and has been hypothesized to cause several chronic diseases, including lung cancer. The purpose of this article is to identify, describe, and critically examine the published studies on the association between C. pneumoniae infection and risk of lung cancer. In the six studies identified, previous C. pneumoniae infection was defined on the basis of serologic criteria, which varied between studies. All studies reported elevated relative risk estimates for the association of serologic evidence of infection and risk of lung cancer. The three studies in which past infection was defined based on testing of prediagnostic blood specimens tended to have weaker results (odds ratio range, 1.2-2.1) than those based on postdiagnostic blood specimens (odds ratio range, 1.4-9.9). Selection bias, measurement error, and inadequate control for confounding are concerns in some of these studies. Nevertheless, results were relatively consistent, supporting a causal association. Inflammation caused by chronic infection with C. pneumoniae may be involved in the carcinogenic process but this relationship will be difficult to further define through serologic data. To better understand the nature of this association, both experimental study designs, such as those based on animal models or randomized controlled antibiotic treatment trials in humans, and observational study designs (e.g., studies that involve detection of C. pneumoniae in pulmonary specimens obtained before cancer onset) could be explored and may shed additional light on this important association.

Prior lung disease and risk of lung cancer in a large prospective study

AbstractObjectives: While 75-90% of people who develop lung cancer are smokers, only a small proportion of smokers develop lung cancer. Identifying factors that increase a smokers risk of developing lung cancer may help scientists to better understand the etiology of lung cancer and more effectively target high-risk groups for screening. Methods: Information on physician-diagnosed non-malignant lung diseases [asbestosis, asthma, chronic bronchitis or emphysema (CB/E), pneumonia, and tuberculosis] was obtained at baseline from 17,698 men and women involved in CARET, a randomized lung cancer prevention trial of beta-carotene and vitamin A among heavy smokers and asbestos-exposed workers. Hazard ratios for lung cancer were estimated through Cox regression models, after controlling for potential confounding factors, included smoking. Analyses were restricted to former and current smokers. Results: During a median follow up of 9.1 years, 1028 cases of lung cancer occurred. Those who developed lung cancer were more likely to report a history of CB/E than controls (adjusted HR = 1.29, 95% CI: 1.09-1.53). In subgroup analyses, the association between a history of CB/E and lung cancer was stronger for those who were younger at diagnosis/reference, men in the heavy smoker cohort, former smokers, and those with squamous cell carcinomas. There was little association between a history of other lung diseases and lung cancer. Conclusions: Smokers with a history of CB/E may be at higher risk of developing lung cancer, independent of their smoking history.

The association of dietary fat and plant foods with endometrial cancer (United States)

AbstractObjectives: To examine the associations of dietary fat and selected plant foods with endometrial cancer in a population-based case–control study. Methods: Six hundred and seventy-nine incident cases of endometrial cancer diagnosed between 1985 and 1991, and 944 population-based controls completed a 98-item semi-quantitative food-frequency questionnaire and a detailed in-person interview which collected information on endometrial cancer risk factors. Logistic regression was used to estimate odds ratios (OR) and their 95% confidence intervals (CI) of endometrial cancer, adjusted for age, county, energy intake, hormone use, smoking and, in separate models, for body mass index (BMI: kg/m2). Results: Percent energy from fat was associated with an increased risk of endometrial cancer (highest quintile cf. lowest: OR = 1.8, 95% CI 1.3–2.6), with saturated and monounsaturated fats being the main contributors of risk. There was a stronger association between dietary fat and endometrial cancer among groups with higher circulating estrogen levels (i.e. women with higher BMI, users of unopposed estrogens, non-smokers, and younger age at menarche). Consumption of fruits or vegetables was inversely associated with endometrial cancer risk (highest quintile cf. lowest: OR = 0.65, 95% CI 0.46–0.93 and OR = 0.61, 95% CI 0.43–0.88, respectively). Further adjustment for BMI resulted in little or no attenuation of the ORs and associated CIs. Conclusions: These results provide support for the theory that a low-fat, high-fruit and high-vegetable diet may reduce the risk of endometrial cancer, and that these dietary factors may act independently of the effect of BMI.

Effects of physical activity intensity, frequency, and activity type on 10-y weight change in middle-aged men and women.

BACKGROUND:Increased physical activity is often recommended for weight maintenance and loss.OBJECTIVE:To examine how intensity, frequency, and type of recreational physical activity are associated with weight gain attenuation over a 10-y period.PARTICIPANTS:Over 15 000 adults between 53 and 57 y living in western Washington State recruited between 2000 and 2002.MEASUREMENTS:Self-reported measures of physical activity (using a questionnaire), height, and weight.METHODS:We examined associations between physical activity and weight change after age 45 y. All analyses controlled for age at baseline, weight at age 45 y (continuous), diet, education, smoking, and weight change between ages 30 and 45 y, and were stratified by sex and body mass index (BMI) at age 45 y (normal weight, overweight, or obese).RESULTS:Increasing MET-hours and sessions per week of high-, moderate- and low-intensity activities over 10 y were inversely related to weight gain after age 45 y. Generally, associations were stronger for women than for men and for obese compared to normal weight or overweight individuals. Obese women and men who participated in 75–100 min per week of fast walking gained 9 and 5 pound less than nonwalkers, respectively, and lesser amounts in normal weight and overweight women and men. Jogging, aerobics, and fast cycling were associated with weight gain attenuation in most sex and age 45 y BMI groups, while slow walking, swimming, and weight lifting were not.CONCLUSIONS:In this free-living population, long-term, regular physical activity, particularly common activities carried out at a moderate intensity such as walking, prevented some of the weight gain associated with aging.

Assessing nonresponse bias at follow-up in a large prospective cohort of relatively young and mobile military service members

BackgroundNonresponse bias in a longitudinal study could affect the magnitude and direction of measures of association. We identified sociodemographic, behavioral, military, and health-related predictors of response to the first follow-up questionnaire in a large military cohort and assessed the extent to which nonresponse biased measures of association.MethodsData are from the baseline and first follow-up survey of the Millennium Cohort Study. Seventy-six thousand, seven hundred and seventy-five eligible individuals completed the baseline survey and were presumed alive at the time of follow-up; of these, 54,960 (71.6%) completed the first follow-up survey. Logistic regression models were used to calculate inverse probability weights using propensity scores.ResultsCharacteristics associated with a greater probability of response included female gender, older age, higher education level, officer rank, active-duty status, and a self-reported history of military exposures. Ever smokers, those with a history of chronic alcohol consumption or a major depressive disorder, and those separated from the military at follow-up had a lower probability of response. Nonresponse to the follow-up questionnaire did not result in appreciable bias; bias was greatest in subgroups with small numbers.ConclusionsThese findings suggest that prospective analyses from this cohort are not substantially biased by non-response at the first follow-up assessment.