Analyzing left-truncated right-censored data with uncertain onset time with parametric models

Prevalent sampling is an efficient and focused approach to the study of the natural history of disease. Right-censored time-to-event data observed from prospective prevalent cohort studies are often subject to left-truncated sampling. Left-truncated samples are not randomly selected from the population of interest and have a selection bias. Extensive studies have focused on estimating the unbiased distribution given left-truncated samples. However, in many applications, the exact date of disease onset was not observed. For example, in an HIV infection study, the exact HIV infection time is not observable. However, it is known that the HIV infection date occurred between two observable dates. Meeting these challenges motivated our study. We propose parametric models to estimate the unbiased distribution of left-truncated, right-censored time-to-event data with uncertain onset times. We first consider data from a length-biased sampling, a specific case in left-truncated samplings. Then we extend the proposed method to general left-truncated sampling. With a parametric model, we construct the full likelihood, given a biased sample with unobservable onset of disease. The parameters are estimated through the maximization of the constructed likelihood by adjusting the selection bias and unobservable exact onset. Simulations are conducted to evaluate the finite sample performance of the proposed methods. We apply the proposed method to an HIV infection study, estimating the unbiased survival function and covariance coefficients. ^

An investigation into the relationship between screen time, consumption of advertised foods, and physical activity among Texas 4th grade elementary school children

Background. The high prevalence of obesity among children has spurred creation of a list of possible causative factors, including the advertising of foods of minimal nutritional value, a decrease in physical activity, and increased media use. Few studies show prevalence rates of these factors among large cohorts of children. ^ Methods. Using data from the 2004-2005 School Physical Activity and Nutrition project (SPAN), a secondary analysis of 7907 4th-grade children (mean age 9.74 years) was conducted. In addition, a comic-book–based intervention that addressed advertised food consumption, physical activity, and media use was developed and evaluated using a pre-post test design among 4th-grade children in an urban school district. ^ Results. Among a cohort of 4th-grade children across the state of Texas, children who had more than 2 hours of video game or computer time the previous day were more than twice as likely to drink soda and eat candy or pastries. In addition, children who watched more than 2 hours of TV the previous day were more than three times as likely to consume chips, punch, soda, candy, frozen desserts, or pastries (AOR 3.41, 95% CI: 1.58, 7.37). A comic-book based intervention held great promise and acceptance among 4th-grade children. Outcome evaluation showed that while results moved in a positive direction, they were not statistically significant. ^ Conclusion. Statistically significant associations were found between screen time and eating various types of advertised food. The comic book intervention was widely accepted by the children exposed to it, and pre-post surveys indicated they moved constructs in a positive direction. Further research is needed to look at more specific ways in which children are exposed to TV, and the relationship of the TV viewing time with their consumption of advertised foods. In addition, researchers should look at comic book interventions more closely and attempt to utilize them in more in studies with a longer follow-up time. ^

Integrating diabetes self-management with the health goals of older adults: A qualitative exploration

Objective. This study investigates the life and health goals of older adults with diabetes, and explores the factors that influence their diabetes self-management. Methods: Qualitative in-depth interviews were conducted with 24 older adults with diabetes and other morbid conditions and/or their caregivers, when appropriate. ^ Results. Participants’ provided a consistent set of responses when describing life and health goals. Participants described goals for longevity, better physical functioning, spending time with family, or maintaining independence. Diabetes discordant conditions, but not diabetes, were seen as barriers to life goals for participants with functional impairments. Functionally independent participants described additional health goals that related to diabetes self-management as diabetes was seen often a barrier to life goals. Caregivers, co-morbid conditions, denial and retirement were among the factors that influenced initiation of diabetes self-management. ^ Conclusion. Participants endorsed health goals and diabetes self-management practices that they believed would help them accomplish their life goals. Functional capabilities and social support were key factors in the relationship between diabetes self-management and their broader goals. ^ Practice implications. When planning diabetes treatments, clinicians, patients and caregivers should discuss the relationship between diabetes self-management and health and life goals as well as the affects of functional limitations and caregiver support.^

Factors influencing participation in individuals with disability: A secondary data analysis

Individuals with disabilities face numerous barriers to participation due to biological and physical characteristics of the disability as well as social and environmental factors. Participation can be impacted on all levels from societal, to activities of daily living, exercise, education, and interpersonal relationships. This study evaluated the impact of pain, mood, depression, quality of life and fatigue on participation for individuals with mobility impairments. This cross sectional study derives from self-report data collected from a wheelchair using sample. Bivariate correlational and multivariate analysis were employed to examine the relationship between pain, quality of life, positive and negative mood, fatigue, and depression with participation while controlling for relevant socio-demographic variables (sex, age, time with disability, race, and education). Results from the 122 respondents with mobility impairments demonstrated that after controlling for socio-demographic characteristics in the full model, 20% of the variance in participation scores were accounted for by pain, quality of life, positive and negative mood, and depression. Notably, quality of life emerged as being the single variable that was significantly related to participation in the full model. Contrary to other studies, pain did not appear to significantly impact participation outcomes for wheelchair users in this sample. Participation is an emerging area of interest among rehabilitation and disability researchers, and results of this study provide compelling evidence that several psychosocial factors are related to participation. This area of inquiry warrants further study, as many of the psychosocial variables identified in this study (mood, depression, quality of life) may be amenable to intervention, which may also positively influence participation.^

A comparison of risky sexual behaviors between older and younger men who have sex with men in Houston, TX

Objectives. This study estimated the prevalence of risky sexual behaviors of older (≥ years old) and younger (18-24 years) men who have sex with men (MSM) in Houston, TX and compared the prevalence of these behaviors between the two age cohorts. ^ Methods. Data used in this analysis were from the third MSM cycle of the National HIV Behavioral Surveillance Study. There were 80 older and 119 younger MSM who met the eligibility criteria. Bivariate and Multivariate analysis were performed to compare risky sexual behaviors from the past 12 months and at last sexual encounter between the two age cohorts. ^ Results. OMSM were more likely to be Non-Hispanic White (AOR=4.17; CI: 1.46, 11.89), to have a household income last year greater than $75,000 (AOR=3.59; CI: 1.12, 11.55), and to self-report HIV-positive (AOR=7.35; CI: 2.69, 20.10) than YMSM. OMSM were less like to have had anal sex (AOR=0.11; CI: 0.04, 0.29) or a main sex partner (AOR=0.2; CI: 0.09, 0.45) than YMSM in the past 12 months. Among MSM who had anal sex at last sexual encounter, OMSM were more likely to have not used a condom the entire time regardless of partner type (AOR=3.64; CI: 1.54, 8.61), not used a condom the entire time with a causal sex partner (AOR=7.72; CI: 1.76, 33.92), had unprotected insertive anal intercourse (AOR=2.92; CI: 1.1, 7.75), and used alcohol before or during sex (AOR=5.33; CI: 2.15, 13.2) than YMSM. YMSM and OMSM did not different significantly in knowledge of last sex partner's HIV status. ^ Conclusions. This is not a homogeneous sample of OMSM and risky sexual behaviors vary within the group. There were many similarities in risk behavior between OMSM and YMSM but also some key differences in partner type and condom use indicating a need for increased age-appropriate health promotion programs to limit a potential increase in HIV infection among OMSM. ^