A brief conceptual tutorial on multilevel analysis in social epidemiology: investigating contextual phenomena in different groups of people

• Published in: Journal of epidemiology and community health (1979) Vol. 59; no. 9; pp. 729 - 736
• Main Authors: Merlo, Juan, Yang, Min, Chaix, Basile, Lynch, John, Råstam, Lennart
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd 01.09.2005; BMJ Publishing Group; BMJ; BMJ Publishing Group LTD; BMJ Group
• Subjects: Adult; Age; AHM; Analysis of Variance; Antihypertensive Agents; antihypertensive medication; Biological and medical sciences; Blood Pressure; BMI; Body Mass Index; Cluster Analysis; Coefficients; Community health; Epidemiologic Methods; Epidemiology; General aspects; Health Sciences; Health Status; Humans; Hypertension; Hälsovetenskap; Life Sciences; Medical and Health Sciences; Medical sciences; Medicin och hälsovetenskap; Middle Aged; Miscellaneous; MLRA; Modeling; Models, Statistical; multilevel analysis; Multilevel models; multilevel regression analysis; neighbourhoods; Population; Public health; Public health. Hygiene; Public health. Hygiene-occupational medicine; Regression Analysis; Regression coefficients; Research design; Research Support, Non-U.S. Gov't; Residence Chara; Residence Characteristics; Residence Characteristics - statistics & numerical data; Santé publique et épidémiologie; SBP; social epidemiology; Statistical variance; Studies; systolic blood pressure; Theory and Methods; Variables; variance partition coefficient; VPC; Medicine; Multilevel analysis; Theory; Social analysis; Social medicine; Conceptual analysis; Epidemiology; Public health
• ISSN: 0143-005X; 1470-2738; 1470-2738
• DOI: 10.1136/jech.2004.023929

Study objective: (1) To provide a didactic and conceptual (rather than mathematical) link between multilevel regression analysis (MLRA) and social epidemiological concepts. (2) To develop an epidemiological vision of MLRA focused on measures of health variation and clustering of individual health status within areas, which is useful to operationalise the notion of “contextual phenomenon”. The paper shows how to investigate (1) whether there is clustering within neighbourhoods, (2) to which extent neighbourhood level differences are explained by the individual composition of the neighbourhoods, (3) whether the contextual phenomenon differs in magnitude for different groups of people, and whether neighbourhood context modifies individual level associations, and (4) whether variations in health status are dependent on individual level characteristics. Design and participants: Simulated data are used on systolic blood pressure (SBP), age, body mass index (BMI), and antihypertensive medication (AHM) ascribed to 25 000 subjects in 39 neighbourhoods of an imaginary city. Rather than assessing neighbourhood variables, the paper concentrated on SBP variance between individuals and neighbourhoods as a function of individual BMI. Results: The variance partition coefficient (VPC) showed that clustering of SBP within neighbourhoods was greater for people with a higher BMI. The composition of the neighbourhoods with respect to age, AHM use, and BMI explained about one fourth of the neighbourhood differences in SBP. Neighbourhood context modified the individual level association between BMI and SBP. Individual level differences in SBP within neighbourhoods were larger for people with a higher BMI. Conclusions: Statistical measures of multilevel variations can effectively quantify contextual effects in different groups of people, which is a relevant issue for understanding health inequalities.