A Comparison of Disease Burden Between Twins and Control Pairs in Medicare: Quantification of Heredity's Role in Human Health.

To quantify heredity's effects on the burden of illness in the Medicare population, this study linked information between participants in a research twin registry to a comprehensive set of Medicare claims. To calculate disease categories, the authors used the Centers for Medicare & Medicaid Services Hierarchical Conditions Categories (HCC) model that was developed to risk adjust Medicare's capitation payments to private health care plans based on the health expenditure risk of their enrollees. Using the Medicare database, 2 sets of unrelated but demographically matched control pairs (MCPs) were generated, one specific for the monozygotic twin population and the second specific for the dizygotic twin population. The concordance and correlation rates of the 70 HCC categories for the 2 twin populations, in comparison to their corresponding MCP, was then calculated using Medicare claims data from 1991 through 2011. When indicated, HCCs for which there was a statistically significant difference between the twin and corresponding MCP control group were analyzed by calculating concordance and correlation rates of the International Classification of Diseases, Ninth Revision codes that compose the HCC. Findings reveal that monozygotic twins share 6.5% more HCC disease categories than their MCP while dizygotic twins share 3.8% more HCC disease categories than their MCP. Atrial fibrillation is a highly heritable disease category, a finding consistent with prior literature describing the heritability of the cardiac arrhythmias. These findings are consistent with qualitative assessments of heredity's role found in previous models of population health, and provide both novel methods and quantitative evidence to support future model development.

Health-related and sociodemographic risk factors for disability pension due to low back disorders: a 30-year prospective Finnish Twin Cohort Study.

OBJECTIVES: To investigate health-related and sociodemographic risk factors for disability pensions (DP) due to low back disorders (LBD). METHODS: Questionnaire data in 1975 of the Finnish Twin Cohort Study with record linkage to information on DP due to LBD from the official pension registers during follow-up 1975 to 2004 was analyzed with Cox proportional hazard models. RESULTS: Musculoskeletal pain (Hazards Ratio [HR] = 2.36 to 2.39; 95% CI 1.97 to 2.88), smoking (HR = 1.82; 1.49 to 2.22), frequent analgesics use (HR = 1.67; 1.38 to 2.02), and presence of other chronic disease (HR = 1.44; 1.22 to 1.70) increased the risk for DP due to LBD. Years of education decreased the risk (HR = 0.81; 0.77 to 0.85). Associations remained significant when adjusted for familial background. CONCLUSIONS: Health-related and sociodemographic risk factors for DP due to LBD can be identified early in life, and they seem independent from familial effects.

Genetic effects on physical health: lower at higher income levels.

Given the robust finding that people in higher income groups tend to experience better physical health, there is interest in identifying mechanisms underlying this gradient. Using a nationwide sample of 719 twin pairs from the National Survey of Midlife Development in the United States, we investigated the possibility that gene-environment interaction underlies the income-health gradient. We observed that genetic variance associated with 2 measures of physical health, number of chronic illnesses and body mass index, each declined significantly with increasing income. This interaction effect could not be removed by adjusting income for the presence of health insurance coverage and education, suggesting that the interaction is not simply a result of differences in levels of those characteristics with income.