William A. Satariano

Causes and consequences of comorbidity: a review.

A literature search was carried out to identify and summarize the existing information on causes and consequences of comorbidity of chronic somatic diseases. A selection of 82 articles met our inclusion criteria. Very little work has been done on the causes of comorbidity. On the other hand, much work has been done on consequences of comorbidity, although comorbidity is seldom the main subject of study. We found comorbidity in general to be associated with mortality, quality of life, and health care. The consequences of specific disease combinations, however, depended on many factors. We recommend more etiological studies on shared risk factors, especially for those comorbidities that occur at a higher rate than expected. New insights in this field can lead to better prevention strategies. Health care workers need to take comorbid diseases into account in monitoring and treating patients. Future studies on consequences of comorbidity should investigate specific disease combinations.

Original articleCauses and consequences of comorbidity: A review

A literature search was carried out to identify and summarize the existing information on causes and consequences of comorbidity of chronic somatic diseases. A selection of 82 articles met our inclusion criteria. Very little work has been done on the causes of comorbidity. On the other hand, much work has been done on consequences of comorbidity, although comorbidity is seldom the main subject of study. We found comorbidity in general to be associated with mortality, quality of life, and health care. The consequences of specific disease combinations, however, depended on many factors. We recommend more etiological studies on shared risk factors, especially for those comorbidities that occur at a higher rate than expected. New insights in this field can lead to better prevention strategies. Health care workers need to take comorbid diseases into account in monitoring and treating patients. Future studies on consequences of comorbidity should investigate specific disease combinations.

To GEE or not to GEE: comparing population average and mixed models for estimating the associations between neighborhood risk factors and health.

Two modeling approaches are commonly used to estimate the associations between neighborhood characteristics and individual-level health outcomes in multilevel studies (subjects within neighborhoods). Random effects models (or mixed models) use maximum likelihood estimation. Population average models typically use a generalized estimating equation (GEE) approach. These methods are used in place of basic regression approaches because the health of residents in the same neighborhood may be correlated, thus violating independence assumptions made by traditional regression procedures. This violation is particularly relevant to estimates of the variability of estimates. Though the literature appears to favor the mixed-model approach, little theoretical guidance has been offered to justify this choice. In this paper, we review the assumptions behind the estimates and inference provided by these 2 approaches. We propose a perspective that treats regression models for what they are in most circumstances: reasonable approximations of some true underlying relationship. We argue in general that mixed models involve unverifiable assumptions on the data-generating distribution, which lead to potentially misleading estimates and biased inference. We conclude that the estimation-equation approach of population average models provides a more useful approximation of the truth.

A Longitudinal Study of Cardiorespiratory Fitness and Cognitive Function in Healthy Older Adults

OBJECTIVES: To determine whether cardiorespiratory fitness at baseline is associated with maintenance of cognitive function over 6 years or with level of cognitive function on tests performed 6 years later in a longitudinal study of healthy older people.

The process of recovery from breast cancer for younger and older patients. Changes during the first year

A representative community sample of 274 breast cancer (BC) patients from the Metropolitan Detroit Cancer‐Surveillance System was studied longitudinally during the year after their BC diagnosis. The adjustment of these patients to their disease was examined in terms of (1) the changes in their physical and mental health functioning; and (2) the factors that predict or facilitate the recovery process, including the independent and interactive effects of age. Comparison of the outcomes at 4 and 10 months after diagnosis manifested a significant and consistent improvement in physical functioning. In contrast, there was an absence of any improvement in indicators of mental health and well‐being. Whereas the cross‐sectional analyses demonstrated that stage of disease had an impact on physical impairment, the longitudinal analyses revealed that physical impairment at time 1 was the significant predictor of deteriorating mental health at time 2. Furthermore, younger age was shown to exacerbate the impact of impairment on mental health. The more seriously impaired younger patients experienced significantly greater deterioration in their mental health and well‐being than similarly impaired older patients. However, older age was found to exacerbate the impact of more extensive surgery on symptoms that produce limitations in activity.

Comorbidity and survival in HIV-Infected men in the San Francisco Men's Health Survey☆

The course of disease associated with infection with the human immunodeficiency virus varies widely. Some patients deteriorate rapidly, while others live for years, even after an illness that defines the acquired immunodeficiency syndrome (AIDS). In this study, comorbidity, or the presence of concurrent health problems, was investigated prospectively as a possible co-factor for different rates of decline in 395 homosexual/bisexual men in the San Francisco Mens Health Study (SFMHS) who were infected with the human immunodeficiency virus (HIV). Comorbidity data obtained from baseline interviews included both chronic and infectious diseases as well as depression. Smoking, alcohol, and drug use were also examined. The most prevalent comorbid conditions were sexually transmitted diseases (90%) and hepatitis B infection (76%). Most chronic and acute concurrent health conditions were not significant discrete predictors of survival to AIDS or death after controlling for immune status and markers of disease progression. Significantly, other risk factors (e.g., depression and smoking) were found to be associated with more rapid progression. Men with symptoms of depression had a higher risk of progression of AIDS diagnosis; the relative hazard (RH) was 1.4 (95% confidence interval [CI], 1.00-2.08); smoking was associated with higher risk of death (RH, 1.6; 95% CI, 1.20-2.17). Older age was marginally associated with poorer survival to death. No associations were found between survival and alcohol and drug use.

Cause of death in men diagnosed with prostate carcinoma

Prostate carcinoma is one of the leading causes of death in men. Although the mortality rate is high, it still may underestimate the number of deaths associated with the disease. This study was conducted to compare causes of death among men previously diagnosed with prostate carcinoma and to examine the extent to which differences in cause of death (death from prostate carcinoma vs. death from other causes) varied by age, race, clinical factors, and comorbid conditions.

Comorbidity and breast cancer survival: a comparison between black and white women.

The presence of concurrent health conditions (comorbidity) at the time of breast cancer diagnosis has an adverse effect on survival. It is unclear, however, whether the strength of the association between comorbidity and survival varies in different populations of breast cancer patients. It is necessary, therefore, to establish (1) whether a comorbidity index derived from a general population of patients (mostly white) would predict survival in a black population, and (2) whether comorbidity would have the same degree of relationship to mortality in black as in white populations. We studied 1196 breast cancer patients who were members of the Kaiser Permanente Medical Care Program and were diagnosed with local (n = 708), regional (n = 446), or remote (n = 49) stage breast cancer from 1973 to 1986. Mortality follow-up was completed to December 1994. Ten-year survival was studied in relation to the Charlson comorbidity index for black women and for white women, and for both groups of women combined. Compared to women with a Charlson comorbidity score of 0 (no comorbidity), patients with scores of 1, 2, and 3+ had risk ratios for ten-year mortality of 1.23 (P = 0.10), 2.58 (P < 0.001), and 3.44 (P < 0.001), respectively. This pattern of risk associated with comorbidity was similar to that found in the original Charlson study. The pattern of risk ratios for different levels of comorbidity was very similar for black and white patients. The results confirm previous studies indicating that comorbidity (in particular, the Charlson Comorbidity Index) predicts the survival of women with breast cancer, independently of other factors, such as stage of breast cancer at diagnosis. The Charlson index has prognostic significance for both black and white populations. Research is needed to determine whether the Charlson index can be improved by including health conditions that are particularly prevalent or severe in specific subgroups of women.

Promoting physical activity among older adults: from ecology to the individual.

The promotion of physical activity in older populations holds the promise of promoting health and reducing the risk of disablement. Individual- and community-based programs are often presented as being distinct and, in some cases, antithetical. The objective of this paper is to illustrate, through the use of an ecologic model, that individual- and community-based programs are complementary. The following topics are discussed: (1). the development of transdisciplinary theories; (2). the establishment of better measures to address the linkages across individual behavior, group behavior, the built environment, and the temporal sequence of biological, behavioral, and environmental factors; (3). the translation of research into practice and policies; and (4). the training of a new generation of scholars and practitioners to develop and execute research, practice, and policy agendas in this area. An ecologic model fosters a comprehensive agenda based on biological, behavioral, and environmental factors. The study of the interaction of the individual with the environment is challenging but potentially more important than the study of the role of the individual or the environment alone in the promotion of physical activity.

Reasons given by older people for limitation or avoidance of leisure time physical activity.

OBJECTIVES: This study investigates reasons given by older people for limitation or avoidance of physical exercise.