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We review agent-based models (ABM) of human migration with respect to their decision-making rules. The most prominent behavioural theories used as decision rules are the random utility theory, as implemented in the discrete choice model, and the theory of planned behaviour. We identify the critical choices that must be made in developing an ABM, namely the modelling of decision processes and social networks. We also discuss two challenges that hamper the widespread use of ABM in the study of migration and, more broadly, demography and the social sciences: (a) the choice and the operationalisation of a behavioural theory (decision-making and social interaction) and (b) the selection of empirical evidence to validate the model. We offer advice on how these challenges might be overcome.

International migration affects all countries of the world. It is anticipated that in an increasingly interconnected world, migration will increase. People migrate for various reasons ranging from pursuing a better life to reuniting with families to escaping war and natural disaster. While progress has been made in understanding the drivers of migration, there is still much to be learned to monitor and predict migration flows. We do not know how many people leave their country to settle elsewhere, either temporarily or permanently, and we know little about these migrants. The impact of migration on the individual and on sending and receiving communities and countries is only partly understood. The economic effects can be very different from the impacts on society and culture. We advocate a comprehensive approach to the study of migration that involves (a) better measurement, (b) greater insight into factors and actors that either initiate migration flows or perpetuate and reinforce flows, (c) greater insight into the emergence of migration systems, i.e. systems linking people, families and communities in different countries, (d) greater insight into the consequences of migration for the individual, communities and society at large, and (e) much better performance in predicting migration flows and migrant characteristics. The lack of knowledge creates huge systemic risks and uncertainties and frustrates the formation of effective policies. In this contribution, we review what we know and what we should know. We conclude with priorities for data collection, research and training.

Increasing BMI causes concerns about the consequences for health care. Decreasing cardiovascular mortality has lowered obesity‐related mortality, extending duration of disability. We hypothesized increased duration of disability among overweight and obese individuals. We estimated age‐, risk‐, and state‐dependent probabilities of activities of daily living (ADL) disability and death and calculated multistate life tables, resulting in the comprehensive measure of life years with and without ADL disability. We used prospective data of 16,176 white adults of the Health and Retirement Survey (HRS). Exposures were self‐reported BMI and for comparison smoking status and levels of education. Outcomes were years to live with and without ADL disability at age 55. The reference categories were high normal weight (BMI: 23–24.9), nonsmoking and high education. Mild obesity (BMI: 30–34.9) did not change total life expectancy (LE) but exchanged disabled for disability‐free years. Mild obesity decreased disability‐free LE with 2.7 (95% confidence limits 1.2; 3.2) year but increased LE with disability with 2.0 (0.6; 3.4) years among men. Among women, BMI of 30 to 34.9 decreased disability‐free LE with 3.6 (2.1; 5.1) year but increased LE with disability with 3.2 (1.6;4.8) years. Overweight (BMI: 25–29.9) increases LE with disability for women only, by 2.1 (0.8; 3.3) years). Smoking compressed disability by high mortality. Smoking decreased LE with 7.2 years, and LE with disability with 1.3 (0.5; 2.5) years (men) and 1.4 (0.3; 2.6) years (women). A lower education decreased disability‐free life, but not duration of ADL disability. In the aging baby boom, higher BMI will further increase care dependence.

Smoking, by shortening life, decreases both the probability and duration of cardiovascular disease throughout the life course. Non-smokers live many years longer and longer free of cardiovascular disease than smokers, but at the end of their life non-smokers will have lived longer with cardiovascular disease.

Improved health may extend or shorten the duration of cognitive impairment by postponing incidence or death. We assess the duration of cognitive impairment in the US Health and Retirement Study (1992–2004) by self reported BMI, smoking and levels of education in men and women and three ethnic groups. We define multistate life tables by the transition rates to cognitive impairment, recovery and death and estimate Cox proportional hazard ratios for the studied determinants. 95% confidence intervals are obtained by bootstrapping. 55 year old white men and women expect to live 25.4 and 30.0 years, of which 1.7 [95% confidence intervals 1.5; 1.9] years and 2.7 [2.4; 2.9] years with cognitive impairment. Both black men and women live 3.7 [2.9; 4.5] years longer with cognitive impairment than whites, Hispanic men and women 3.2 [1.9; 4.6] and 5.8 [4.2; 7.5] years. BMI makes no difference. Smoking decreases the duration of cognitive impairment with 0.8 [0.4; 1.3] years by high mortality. Highly educated men and women live longer, but 1.6 years [1.1; 2.2] and 1.9 years [1.6; 2.6] shorter with cognitive impairment than lowly educated men and women. The effect of education is more pronounced among ethnic minorities. Higher life expectancy goes together with a longer period of cognitive impairment, but not for higher levels of education: that extends life in good cognitive health but shortens the period of cognitive impairment. The increased duration of cognitive impairment in minority ethnic groups needs further study, also in Europe.

Objective: To investigate the degree of individual heterogeneity related to complex dietary behaviour and to further examine the associations of different dietary compositions with selected characteristics. Design: Latent class analysis was applied to data from the recent cross-sectional National Family Health Survey that collected information on the intake frequency of selected foods. Different responses regarding intake frequency were condensed into a set of five meaningful latent clusters representing different dietary patterns and these clusters were then labelled based on the reported degree of diet mixing. Setting: Indian states. Subjects: In total, 90 180 women aged 15 -49 years. Results: Three clusters were predominantly non-vegetarian and two were vegetarian. A very high or high mixed-diet pattern was observed particularly in the southern and a few north-eastern states. Many women in the very high mixed-diet cluster consumed mostly non-green/leafy vegetables on a daily basis, and fruits and other non-vegetarian diet on a weekly basis. In contrast, those in the low mixed-diet cluster consumed more than three-fifths of the major vegetarian diet ingredients alone on a daily basis. The affluent group that represented the low mixed-diet cluster were primarily vegetarians and those who represented the very high mixed-diet cluster were mostly non-vegetarians. The significant interrelationships of different characteristics highlight not only socio-economic, spatial and cultural disparities related to dietary practices, but also the substantial heterogeneity in diet mixing behaviour. Conclusions: The results of this study confirmed our hypothesis of heterogeneous dietary behaviour of Indian women and yielded useful policy-oriented results which might be difficult to establish otherwise.

IntroductionThere have been recent reports about a decline in dementia incidence, but only little is known about trends in the mortality of patients with dementia. Only the simultaneous analysis of both trends can inform whether the reported decline in dementia has led to a compression of dementia into higher ages.MethodsWe used health claims data from the largest public health insurer in Germany over the two time periods 2004/07 and 2007/10. Dementia was defined according to the International Classification of Disease 10th revision (ICD-10) numbers G30, G31.0, G31.82, G23.1, F00, F01, F02, F03 and F05.1 or by a prescription of cholinesterase inhibitors or memantine or both. In the two time periods, we observed 502,065 person-years of exposure and 10,881 incident dementia cases and 10,013 person-years of exposure among the newly demented and 3049 deaths. We estimated the relative risks of the two time periods applying proportional hazard models and calculated years with or without dementia using the illness-death model.ResultsDementia incidence was significantly higher in 2006/07 than in 2009/10, whereas mortality with dementia tended to be lower in the first period, albeit statistically significant among women only. Mortality without dementia tended to be higher in the first period for men and remained stable for women. Combining these trends, we found that at age 65 remaining life years with dementia were compressed by a yearly 0.4 months for men and 1.4 months for women. At the same time, remaining life years without dementia increased by a yearly 1.4 months for men and 1.1 months for women.ConclusionsThis study provides evidence that the increase in dementia-free life years went together with an absolute compression of life years with dementia. This positive trend was particularly strong among women. Results were controlled for trends in multi-morbidity and care need, suggesting that the postponement in dementia incidence is not simply caused by a delay in diagnosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13195-015-0146-x) contains supplementary material, which is available to authorized users.