Population effects on individual systolic blood pressure: a multilevel analysis of the World Health Organization MONICA Project

Distribution of Blood Pressure and Heart Rate Among Adults in Jordan: A National Survey

Knowledge of population distribution of blood pressure is useful for predicting blood pressure related health burden as well as for planning prevention strategy. The aim of this investigation is to determine the distribution of systolic blood pressure (SBP), diastolic blood pressure (DBP), arterial blood pressure (ABP), and heart rate among normotensive adults resident from all regions of Jordan. This study is the first detailed description of these parameters in Jordan at a national level. A total of 14,310 adult males (7,400) and females (6,910) were selected randomly in various regions of Jordan. For each individual, the SBP, DBP, and heart rate were measured three times with 10-15-minute intervals in the sitting position and at the resting state. The ABP was calculated from the measured SBP and DBP. The mean values were distributed according to age and sex. Student's t-test was used for statistical analysis. Males had significantly higher SBP, DBP, ABP, and heart rate values than females. There also was an increase of these values with advancing age. Moreover, cases of hypotension and bradycardia were higher in the female population than in males, whereas cases of hypertension and tachycardia were higher in males. Distribution of blood pressure and heart rate among adults in Jordan was determined. Cases of undiagnosed hypertension, hypotension, and an increase or a decrease in heart rate were detected through our random screening in the target population. Individuals with these abnormalities require further clinical investigations to confirm or exclude these findings.

The association between body mass index and hypertension is different between East and Southeast Asians

BACKGROUND

Few studies have allowed direct comparison of the association between body mass index (BMI; in kg/m2) and hypertension in different Asian ethnicities.

OBJECTIVE

We compared the association of BMI with hypertension in Chinese, Indonesian, and Vietnamese adults and determined BMI cutoffs that best predicted hypertension in these populations.

DESIGN

We included 7562 Chinese, 18,502 Indonesian, and 77,758 Vietnamese participants aged 18-65 y. Blood pressure, weight, and height were measured by trained health workers. To define an optimal BMI cutoff, we computed and searched for the shortest distance on receiver operating characteristic curves.

RESULTS

Despite a low mean BMI, the prevalences of hypertension in Chinese, Indonesian, and Vietnamese men were 22.9%, 24.8%, and 14.4%, respectively, and in women were 16.6%, 26.9%, and 11.7%, respectively. At all BMI levels, the sex-specific prevalence of hypertension was higher in Indonesian adults than in Chinese and Vietnamese adults (P < 0.05 at almost all BMI levels). The overall and stratified analyses suggested optimal BMI cutoffs of 23-24, 21-22.5, and 20.5-21 for Chinese, Indonesian, and Vietnamese adults, respectively. The cutoffs were approximately 0.5-1.0 units higher in women than in men and in the older (41-65 y) than in the younger (18-40 y) participants.

CONCLUSIONS

The study showed an ethnic difference in the BMI-hypertension association and in optimal BMI cutoffs between Chinese, Indonesian, and Vietnamese adults. Country-specific or even country-, sex-, and age-specific BMI cutoffs might be needed to identify persons at high risk of cardiovascular diseases.

School-level contextual factors associated with betel quid chewing among schoolchildren in Taiwan

OBJECTIVES

Previous to this research, no literature had explored the clustering of betel quid chewing at the school-level and the contextual factors contributing to this behavior among elementary schoolchildren. This study therefore examines this in clusters stratified according to school geography and the rate of aboriginal students in each school. Individual-level characteristics are controlled in the study.

METHODS

The data used derive from student and parent surveys of the School Smoking Survey Project from a sampling of third and fourth grade children from 13 elementary schools in Tao-Yuan County, Taiwan (n = 1585). The individual- and school-level characteristics regarding betel quid chewing were estimated using multi-level logistic regression analysis.

RESULTS

Compared to their counterparts, students attending schools with higher percentages of aboriginal students (OR = 3.60, 95% CI: 1.31-9.95), or those schools located in a mountainous region (OR = 2.82, 95% CI: 1.19-6.70), were found to have a greater risk of chewing behavior. Other observed characteristics having a significant relationship to student chewing behavior were drinking alcohol and smoking cigarettes.

CONCLUSIONS

The new findings from this study suggest that the specific school attended is an important point of intervention. Therefore, effective policies and preventive programs should be strongly considered for implementation in schools that are putting students at the greatest risk for betel quid chewing behavior. Our study also confirmed the relationship between betel quid chewing, cigarette smoking, and alcohol drinking, suggesting that multifaceted intervention strategies need to be considered in regard to such behaviors among elementary schoolchildren.

Population health and the hardcore smoker: Geoffrey Rose revisited

The "hardening hypothesis" suggests that as smoking prevalence decreases, lighter smokers will quit first, leaving more "hardcore" smokers in the population. At a population level, however, the weight of evidence suggests that no hardening is occurring. By understanding the lessons from Geoffrey Rose's model of population-level risk factor change, we argue that the hardening of the smoking population is not inevitable. The Rose model predicts that the effect of policy interventions, and changes in social norms, can shift the population-level risk distribution for continuing to be a smoker, making it more likely that all smokers will quit. This analysis also suggests that further reductions in smoking prevalence will not come without further changes in the underlying--and largely cultural--root causes of smoking in a population.

Residential environment and blood pressure in the PRIME Study: is the association mediated by body mass index and waist circumference?

OBJECTIVES

Few studies have examined whether social characteristics of the residential environment are associated with blood pressure after controlling for individual sociodemographic characteristics. Even less is known about the processes by which these associations operate. Therefore, we examined whether distinct dimensions of the residential environment (socioeconomic position and urbanicity) were associated with systolic blood pressure. To better understand the processes involved in the associations between contextual factors and blood pressure, we assessed the extent to which these associations were mediated by body mass index and waist circumference.

METHODS

We analysed data from the PRIME Study (7850, 50-60-year-old men surveyed in 1991-1993 in three French regions and recently geocoded on a local scale). We used multilevel regression models to estimate associations between contextual factors and blood pressure, and path analysis to investigate possible mediators of these associations.

RESULTS

After adjustment for individual socioeconomic variables, systolic blood pressure increased independently with decreasing municipality population density and decreasing neighbourhood educational level. Path analysis indicated that approximately 37% of the association between neighbourhood education and blood pressure was statistically explained by the heavier weight and stronger central adiposity of people from deprived neighbourhoods. Approximately 19% of the association with population density was mediated by anthropometric factors.

CONCLUSIONS

These data suggest that the neighbourhood environment may influence blood pressure; only part of the associations between contextual factors and blood pressure may operate through body weight and body shape modification.

Optimal cutoff values for overweight: using body mass index to predict incidence of hypertension in 18- to 65-year-old Chinese adults

Studies aimed at identifying BMI cutoffs representing increased diseased risk for Asians are typically based on cross-sectional studies. This study determines an optimal BMI cutoff for overweight that represents elevated incidence of hypertension in Chinese adults with data from the China Health and Nutrition Survey 2000-2004 prospective cohort. Cumulative incidence was calculated by dividing new cases of hypertension over the study period by the total at-risk population, aged 18-65 y, in 2000. Sex-specific receiver operating characteristic curves were used to assess the sensitivity and specificity of BMI as a predictor of hypertension incidence. Four-year cumulative incidences of hypertension (13% for women and 19% for men) were related (P < 0.005) to the increase in BMI. The crude area under the curves (AUC) were 0.62 (95% CI: 0.59-0.65) and 0.62 (95% CI: 0.58-0.65) for men and women, respectively; the age-adjusted AUC were 0.68 (95% CI: 0.65-0.70) and 0.71 (95% CI: 0.68-0.74) for men and women, respectively. A BMI of 23.5 kg/m(2) for women and 22.5 kg/m(2) for men provided the highest sensitivity and specificity (60%). The finding was consistent in different age groups. A BMI level of 25 kg/m(2) provided lower sensitivities (36% for women and 29% for men) with higher specificities (80% for women and 85% for men). Our study supported the hypothesis that the BMI cutoff to define overweight should be lower in Chinese than that in Western populations.

A brief conceptual tutorial on multilevel analysis in social epidemiology: interpreting neighbourhood differences and the effect of neighbourhood characteristics on individual health

STUDY OBJECTIVE

Using a conceptual rather than a mathematical approach, this article proposed a link between multilevel regression analysis (MLRA) and social epidemiological concepts. It has been previously explained that the concept of clustering of individual health status within neighbourhoods is useful for operationalising contextual phenomena in social epidemiology. It has been shown that MLRA permits investigating neighbourhood disparities in health without considering any particular neighbourhood characteristic but only information on the neighbourhood to which each person belongs. This article illustrates how to analyse cross level (neighbourhood-individual) interactions, how to investigate associations between neighbourhood characteristics and individual health, and how to use the concept of clustering when interpreting those associations and geographical differences in health.

DESIGN AND PARTICIPANTS

A MLRA was performed using hypothetical data pertaining to systolic blood pressure (SBP) from 25 000 subjects living in the 39 neighbourhoods of an imaginary city. Associations between individual characteristics (age, body mass index (BMI), use of antihypertensive drug, income) or neighbourhood characteristic (neighbourhood income) and SBP were analysed.

RESULTS

About 8% of the individual differences in SBP were located at the neighbourhood level. SBP disparities and clustering of individual SBP within neighbourhoods increased along individual BMI. Neighbourhood low income was associated with increased SBP over and above the effect of individual characteristics, and explained 22% of the neighbourhood differences in SBP among people of normal BMI. This neighbourhood income effect was more intense in overweight people.

CONCLUSIONS

Measures of variance are relevant to understanding geographical and individual disparities in health, and complement the information conveyed by measures of association between neighbourhood characteristics and health.

The role country of birth plays in receiving disability pensions in relation to patterns of health care utilisation and socioeconomic differences: a multilevel analysis of Malmo, Sweden

Background

People of low socioeconomic status have worse health and a higher probability of being granted a disability pension than people of high socioeconomic status. It is also known that public and private general physicians and public and private specialists have varying practices for issuing sick leave certificates (which, if longstanding, may become the basis of disability pensions). However, few studies have investigated the influence of a patient's country of birth in this context.

Methods

We used multilevel logistic regression analysis with individuals (first level) nested within countries of birth (second level). We analysed the entire population between the ages of 40 and 64 years (n = 80 212) in the city of Malmo, Sweden, in 2003, and identified 73% of that population who had visited a physician at least once during that year. We studied the associations between individuals and country of birth socioeconomic characteristics, as well as individual utilisation of different kinds of physicians in relation to having been granted a disability pension.

Results

Living alone (OR_women = 1.72, 95% CI: 1.62–1.82; OR_men = 2.64, 95% CI: 2.46–2.83) and having limited educational achievement (OR_women = 2.14, 95% CI: 2.00–2.29; OR_men = 2.12, 95% CI: 1.98–2.28) were positively associated with having a disability pension. Utilisation of public specialists was associated with a higher probability (OR_women = 2.11, 95% CI: 1.98–2.25; OR_men = 2.16, 95% CI: 2.01–2.32) and utilisation of private GPs with a lower probability (OR_men = 0.76, 95% CI: 0.69–0.83) of having a disability pension. However, these associations differed by countries of birth. Over and above individual socioeconomic status, men from middle income countries had a higher probability of having a disability pension (OR_men = 1.61, 95% CI: 1.06–2.44).

Conclusion

The country of one's birth appears to play a significant role in understanding how individual socioeconomic differences bear on the likelihood of receiving a disability pension and on associated patterns of health care utilisation.

Socioeconomic gradients in the prevalence of cardiovascular disease in Scotland: the roles of composition and context

OBJECTIVE

To investigate whether occupational social class and area deprivation are independently associated with the prevalence of cardiovascular disease (CVD) conditions after adjustment for smoking status.

DESIGN

Stratified multistage random sample analysed using multilevel logistic regression.

PARTICIPANTS

8804 adults aged 18-74 at time of interview in 1998-1999, clustered in 312 small areas. The outcome considered was a self report of doctor diagnosis of one of a number of CVD conditions. The survey also provided information concerning the respondent's occupational social class and current smoking status. The Carstairs score (based on the 1991 census) was used to describe small area deprivation.

MAIN RESULTS

The gradient in CVD prevalence across individual social class was attenuated and became insignificant when area deprivation was considered. The aggregation of individual social class and smoking to the area level increased the correlation with disease prevalence at the individual level.

CONCLUSIONS

Although there is a relation between socioeconomic status and CVD prevalence in Scotland, the relation is dominated by area deprivation. When externally validated deprivation measures are not available, aggregated individual characteristics may show a contextual (as compared with compositional) relation.

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

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.

A brief conceptual tutorial of multilevel analysis in social epidemiology: linking the statistical concept of clustering to the idea of contextual phenomenon

STUDY OBJECTIVE

This didactical essay is directed to readers disposed to approach multilevel regression analysis (MLRA) in a more conceptual than mathematical way. However, it specifically develops an epidemiological vision on multilevel analysis with particular emphasis on measures of health variation (for example, intraclass correlation). Such measures have been underused in the literature as compared with more traditional measures of association (for example, regression coefficients) in the investigation of contextual determinants of health. A link is provided, which will be comprehensible to epidemiologists, between MLRA and social epidemiological concepts, particularly between the statistical idea of clustering and the concept of contextual phenomenon.

DESIGN AND PARTICIPANTS

The study uses an example based on hypothetical data on systolic blood pressure (SBP) from 25,000 people living in 39 neighbourhoods. As the focus is on the empty MLRA model, the study does not use any independent variable but focuses mainly on SBP variance between people and between neighbourhoods.

RESULTS

The intraclass correlation (ICC = 0.08) informed of an appreciable clustering of individual SBP within the neighbourhoods, showing that 8% of the total individual differences in SBP occurred at the neighbourhood level and might be attributable to contextual neighbourhood factors or to the different composition of neighbourhoods.

CONCLUSIONS

The statistical idea of clustering emerges as appropriate for quantifying "contextual phenomena" that is of central relevance in social epidemiology. Both concepts convey that people from the same neighbourhood are more similar to each other than to people from different neighbourhoods with respect to the health outcome variable.

Comparison of a spatial approach with the multilevel approach for investigating place effects on health: the example of healthcare utilisation in France

STUDY OBJECTIVE

Most studies of place effects on health have followed the multilevel analytical approach that investigates geographical variations of health phenomena by fragmenting space into arbitrary areas. This study examined whether analysing geographical variations across continuous space with spatial modelling techniques and contextual indicators that capture space as a continuous dimension surrounding individual residences provided more relevant information on the spatial distribution of outcomes. Healthcare utilisation in France was taken as an illustrative example in comparing the spatial approach with the multilevel approach.

DESIGN

Multilevel and spatial analyses of cross sectional data.

PARTICIPANTS

10,955 beneficiaries of the three principal national health insurance funds, surveyed in 1998 and 2000 on continental France.

MAIN RESULTS

Multilevel models showed significant geographical variations in healthcare utilisation. However, the Moran's I statistic showed spatial autocorrelation unaccounted for by multilevel models. Modelling the correlation between people as a decreasing function of the spatial distance between them, spatial mixed models gave information not only on the magnitude, but also on the scale of spatial variations, and provided more accurate standard errors for risk factors effects. The socioeconomic level of the residential context and the supply of physicians were independently associated with healthcare utilisation. Place indicators better explained spatial variations in healthcare utilisation when measured across continuous space, rather than within administrative areas.

CONCLUSIONS

The kind of conceptualization of space during analysis influences the understanding of place effects on health. In many contextual studies, viewing space as a continuum may yield more relevant information on the spatial distribution of outcomes.

Low adherence with antihypertensives in actual practice: the association with social participation--a multilevel analysis

Background

Low adherence is a key factor in explaining impaired effectiveness and efficiency in the pharmacological treatment of hypertension. However, little is known about which factors determine low adherence in actual practice.

The purpose of this study is to examine whether low social participation is associated with low adherence with antihypertensive medication, and if this association is modified by the municipality of residence.

Methods

1288 users of antihypertensive medication were identified from The Health Survey in Scania 2000, Sweden. The outcome was low adherence with antihypertensives during the last two weeks. Multilevel logistic regression with participants at the first level and municipalities at the second level was used for analyses of the data.

Results

Low social participation was associated with low adherence with antihypertensives during the last two weeks (OR = 2.05, 95% CI: 1.05–3.99), independently of low educational level. However, after additional adjustment for poor self-rated health and poor psychological health, the association between low social participation and low adherence with antihypertensives during the last two weeks remained but was not conclusive (OR = 1.80, 95% CI: 0.90–3.61). Furthermore, the association between low social participation and low adherence with antihypertensives during the last two weeks varied among municipalities in Scania (i.e., cross-level interaction).

Conclusion

Low social participation seems to be associated with low adherence with antihypertensives during the last two weeks, and this association may be modified by the municipality of residence. Future studies aimed at investigating health-related behaviours in general and low adherence with medication in particular might benefit if they consider area of residence.