Gene, environment and cognitive function: a Chinese twin ageing study.

BACKGROUND: the genetic and environmental contributions to cognitive function in the old people have been well addressed for the Western populations using twin modelling showing moderate to high heritability. No similar study has been conducted in the world largest and rapidly ageing Chinese population living under distinct environmental condition as the Western populations. OBJECTIVE: this study aims to explore the genetic and environmental impact on normal cognitive ageing in the Chinese twins. DESIGN/SETTING: cognitive function was measured on 384 complete twin pairs with median age of 50 years for seven cognitive measurements including visuospatial, linguistic skills, naming, memory, attention, abstraction and orientation abilities. Data were analysed by fitting univariate and bivariate twin models to estimate the genetic and environmental components in the variance and co-variance of the cognitive assessments. RESULTS: intra-pair correlation on cognitive measurements was low to moderate in monozygotic twins (0.23-0.41, overall 0.42) and low in dizygotic twins (0.05-0.30, overall 0.31) with the former higher than the latter for each item. Estimate for heritability was moderate for overall cognitive function (0.44, 95% CI: 0.34-0.53) and low to moderate for visuospatial, naming, attention and orientation abilities ranging from 0.28 to 0.38. No genetic contribution was estimated to linguistic skill, abstraction and memory which instead were under low to moderate control by shared environmental factors accounting for 23-33% of the total variances. In contrast, all cognitive performances showed moderate to high influences by the unique environmental factors. CONCLUSIONS: genetic factor and common family environment have a limited contribution to cognitive function in the Chinese adults. Individual unique environment is likely to play a major role in determining the levels of cognitive performance.

The genetic basis for cognitive ability, memory, and depression symptomatology in middle-aged and elderly chinese twins.

The genetic influences on aging-related phenotypes, including cognition and depression, have been well confirmed in the Western populations. We performed the first twin-based analysis on cognitive performance, memory and depression status in middle-aged and elderly Chinese twins, representing the world's largest and most rapidly aging population. The sample consisted of 384 twin pairs with a median age of 50 years. Cognitive function was measured using the Montreal Cognitive Assessment (MoCA) scale; memory was assessed using the revised Wechsler Adult Intelligence scale; depression symptomatology was evaluated by the self-reported 30-item Geriatric Depression (GDS-30)scale. Both univariate and multivariate twin models were fitted to the three phenotypes with full and nested models and compared to select the best fitting models. Univariate analysis showed moderate-to-high genetic influences with heritability 0.44 for cognition and 0.56 for memory. Multivariate analysis by the reduced Cholesky model estimated significant genetic (rG = 0.69) and unique environmental (rE = 0.25) correlation between cognitive ability and memory. The model also estimated weak but significant inverse genetic correlation for depression with cognition (-0.31) and memory (-0.28). No significant unique environmental correlation was found for depression with other two phenotypes. In conclusion, there can be a common genetic architecture for cognitive ability and memory that weakly correlates with depression symptomatology, but in the opposite direction.

Family History, Tobacco Smoking, and Risk of Ischemic Stroke.

BACKGROUND AND PURPOSE: Both genetic factors and smoking are associated with ischemic stroke (IS) risk. However, little is known about the potential interaction of these factors. We aimed to assess whether smoking and a positive family history interact to increase the risk of IS. METHODS: The nationwide prospective study recruited 210,000 men and 300,000 women in 2004 to 2008 at ages 30 to 79 years. During 9.7 years of follow-up, we documented 16,923 and 20,656 incident IS cases in men and women without major chronic diseases at baseline, respectively. Multivariable Cox regression models were used to examine associations between family history and IS. Likelihood ratio tests were used to test the smoking-family history interactions on IS. RESULTS: About 67.8% (n=135,168) of men ever smoked regularly compared with 2.7% (n=7,775) of women. Among men, a significant interaction between family history and smoking on IS was observed (P for interaction=0.03), with more pronounced association between family history and IS among ever-regular smokers (hazard ratio [HR], 1.21; 95% confidence interval [CI], 1.16 to 1.27) than among never-smokers (HR, 1.11; 95% CI, 1.01 to 1.23). The association between family history and IS among ex-smokers after more than 10 years of cessation (HR, 1.01; 95% CI, 0.85 to 1.20) appeared similar to that among never-smokers. Among women, a similar but not significant interaction between family history and smoking on IS was observed. Ever-regular smokers who had a family history of stroke had the highest risk of IS. CONCLUSIONS: Among Chinese men, the association of family history with IS was accentuated by smoking, and such accentuation tended to be lowered by cessation.

Association between Antipsychotic Drugs and Mortality in Older Persons with Alzheimer's Disease: A Systematic Review and Meta-Analysis.

Antipsychotic drugs have been inconsistently associated with death risk of Alzheimer's disease (AD) patients. Herein we review and quantitatively summarize the evidence from epidemiological studies. Pertinent studies were identified by searching PubMed and Cochrane Library Register of Controlled Trials through 20 December 2015. The DerSimonian and Laird random effect model was adopted as the pooling method. Twelve studies from nine articles with 11,463 participants were included. The pooled RR of observational studies was 1.36 (95% CI, 0.83-2.24; I2 = 94.9%) for antipsychotic drugs users versus individuals who were not exposed to antipsychotic drugs. When the three studies that were key contributors to the high heterogeneity were excluded, the pooled RR was 2.08 (95% CI 1.39 to 3.13). The result of one double-blind randomized clinical trial indicated that antipsychotic drugs nearly doubled the risk of death in AD patients. In conclusion, there is no evidence of absence of association between antipsychotic drugs' use with death risk of AD patients. Careful assessments of potential benefits and risks should be made before prescribing antipsychotics for treatment of psychosis symptoms and behavioral problems of AD patients.

[Heritability of serum uric acid in adult twins].

OBJECTIVE: To assess the heritability of serum uric acid in adult, using the classic twin design. METHODS: Adult Twins were recruited from the Qingdao Twin Registry. Uric acid, height, weight were measured. Zygosity in all the same-sex twin pairs was determined by 16 polymorphic markers. Heritability was assessed by structural equation models, with age, gender and body mass index (BMI) included as covariates. RESULTS: In total, 687 twin pairs were available for data analyses, including 420 pairs of monozygotic and 267 pairs of dizygotic twins. After logarithm transformed, uric acid in males (17.47 +/- 1.91) was significantly higher than in females (15.22 +/- 1.70, P < 0.0001). After adjustment on age, sex and BMI, intraclass correlations for uric acid were 0.70 for monozygotic twins and 0.40 for dizygotic twins. The sex-limitation AE model, combining additive genetic and unique environmental factors, could produce the best fit for the data. Heritability estimate for uric acid was 70.5% (95%CI: 65.9 - 74.6), with the proportion of unique environmental effects as 29.5% (95%CI: 25.4 - 34.2). CONCLUSION: Additive genetic effects appeared to be the major contributor to the variation of uric acid in this twins sample being studied.