Prognosis of lean and fat hypertensives

How the Seven Countries Study contributed to the launch and development of cardiovascular epidemiology in Italy. A historical perspective

The Italian research group of the Seven Countries Study of Cardiovascular Diseases (SCS), through the independent use of the national cohorts and data, had the lucky opportunity, starting in the early 1960, to launch the Italian research in epidemiology of cardiovascular diseases (CVD). In this way, the Italian Section of that international study became the first investigation with baseline measurements in various cohorts, subsequent re-examinations, systematic search for morbid events, and follow-up for mortality up to 50 years. A large number of scientific aspects has been tackled including estimates of morbidity and mortality rates, the association of risk factors with cardiovascular events and total mortality, the role of risk factor changes, the use of multivariable models, the role of lifestyle behavior, the determinants of all-cause mortality including risk factors rarely measured in other studies, the identification of characteristics of a condition called Heart Disease of Uncertain Etiology (HDUE), the production of predictive tools for practical use and several other issues. All this has been enhanced by the availability of extremely long follow-up data rarely found in other studies. Field work organization, measurement techniques, diagnostic criteria, data handling and computing had the limitations and difficulties typical of those times, the mid of last century, when CVD epidemiology was at its beginning. All this represented anyhow the start of CVD epidemiology research in the country and was the stimulus to the start of other studies and a valuable collaboration with some of them.

Prevalence and risks of hypertension among Indian tribes and its status among the lean and underweight individuals

OBJECTIVE

With the increased worldwide prevalence of hypertension among the underprivileged populations, fewerstudies have reported such risks among Indian tribes. In the context of high prevalence of undernutrition, no such study has examined hypertension among lean and underweight Indian tribal individuals separately.

METHODS

We selected total samples of 1066 adult males and 1090 adult females in 20-60 years age-group cross-sectionally to examine the status of hypertension and its risks among nine major tribes in three Indian states; separate analyses for lean and underweight tribal individuals were done.

RESULTS

Increased prevalence of hypertension (females, 14.2%; males, 9.3%) was observed among the tribes with the overall percentage of individuals at adversity (hypertensive + isolated hypertensive) at more than 20% (males 20.1%; females 26.5%). Age-group-wise prevalence showed a sharp rise in the prevalence of hypertension in the 40 + year individuals; additionally, this rise was alarming among females. Undernutrition was observed to be a potential risk factor as a remarkable prevalence of hypertension was observed among the undernourished (approximately 9%) and lean tribal participants (12%). Underweight females were observed to be at higher risk. Tribal statuses were observed to be alarming than the national trends due to their very low average BMI along with high average SBP. A curvilinear prevalence of hypertension was observed while comparing through both the nutritional extremes.

CONCLUSION

The increased prevalence and risks of hypertension in the background of lean and underweight status of Indian tribes indicates their epidemiological transition burdened with alarming cardio-metabolic health risks that warrant an early and consistent surveillance.

Association of body mass index with cause specific deaths in Chinese elderly hypertensive patients: Minhang community study

Background

Most studies have suggested that elevated body mass index (BMI) was associated with the risk of death from all cause and from specific causes. However, there was little evidence illustrating the effect of BMI on the mortality in elderly hypertensive patients in Chinese population.

Methods

The information of 10,957 hypertensive patients at baseline not less than 60 years were from Xinzhuang, a town in Minhang district of Shanghai, was extracted from the Electronic Health Record (EHR) system. All study participants were divided into eight categories of baseline BMI (with cut-points at 18, 20, 22, 24, 26, 28 and 30 kg/m²). Relative hazard ratio of death from all cause, cardiovascular and non-cardiovascular cause by baseline BMI groups were calculated, standardized for sex, age, smoking, drinking, physical activity, systolic blood pressure, history of cardiovascular disorders, serum lipid disturbance, diabetes mellitus and antihypertensive drug treatment.

Results

During follow up (median: 3.7 years), 561 deaths occurred. Underweight (BMI<18 kg/m²) was associated with significantly increased mortality from all cause mortality (OR: 2.00; 95% CI: 1.43–2.79) and non cardiovascular mortality (OR: 2.76; 95% CI: 1.87–4.07), but not with cardiovascular mortality. For the cause specific analysis, the underweight was associated significantly with neoplasms (OR: 2.15; 95% CI: 1.16–4.00) and respiratory disorders (OR: 3.41; 95% CI: 1.64–7.06). The results for total mortality and specific cause mortality were not influenced by sex, age and smoking status.

Conclusion

Our study revealed an association between underweight and increased mortality from non-cardiovascular disorders in elderly hypertensive patients in Chinese community. Overweight and obesity were not associated with all cause or cause specific death.

Does Body Mass Index Impact on the Relationship Between Systolic Blood Pressure and Cardiovascular Disease?

Background and Purpose—

Elevated blood pressure and excess body mass index (BMI) are established risk factors for cardiovascular disease (CVD) but controversy exists as to whether, and how, they interact.

Methods—

The interactions between systolic blood pressure and BMI on coronary heart disease, ischemic and hemorrhagic stroke and CVD were examined using data from 419 448 participants (≥30 years) in the Asia-Pacific region. BMI was categorized into 5 groups, using standard criteria, and systolic blood pressure was analyzed both as a categorical and continuous variable. Cox proportional hazard models, stratified by sex and study, were used to estimate hazard ratios, adjusting for age and smoking and the interaction was assessed by likelihood ratio tests.

Results—

During 2.6 million person-years of follow-up, there were 10 877 CVD events. Risks of CVD and subtypes increased monotonically with increasing systolic blood pressure in all BMI subgroups. There was some evidence of a decreasing hazard ratio, per additional 10 mm Hg systolic blood pressure, with increasing BMI, but the differences, although significant, are unlikely to be of clinical relevance. The hazard ratio for CVD was 1.34 (95% CI, 1.32–1.36) overall with individual hazard ratios ranging between 1.28 and 1.36 across all BMI groups. For coronary heart disease, ischemic stroke, and hemorrhagic stroke, the overall hazard ratios per 10 mm Hg systolic blood pressure were 1.24, 1.46, and 1.65, respectively.

Conclusions—

Increased blood pressure is an important determinant of CVD risk irrespective of BMI. Although its effect tends to be weaker in people with relatively high BMI, the difference is not sufficiently great to warrant alterations to existing guidelines.

Blood pressure, body mass index and risk of cardiovascular disease in Chinese men and women

Background

It is still uncertain whether increased blood pressure (BP) has a stronger effect on the risk of cardiovascular disease (CVD) in lean persons than in obese persons. We tested it using a data set collected from a large cohort of Chinese adults.

Methods

Systolic and diastolic BP, body mass index (BMI) and other variables were measured in 169,871 Chinese men and women ≥ 40 years of age in 1991 using standard protocols. Follow-up evaluation was conducted in 1999-2000, with a response rate of 93.4%. Data were analyzed with Cox proportional hazards models.

Results

After adjusted for age, sex, cigarette smoking, alcohol consumption, high school education, physical inactivity, geographic region, and urbanization, we found that the effects of systolic or diastolic BP on risk of CVD generally increased with the increasing BMI levels (underweight, normal, overweight, and obese). For example, hazard ratios (HRs) and 95% confidence interval (CI) per 1- standard deviation (SD) increase in systolic BP within corresponding BMI levels were 1.27(1.21-1.33), 1.45(1.41-1.48), 1.52 (1.45-1.59) and 1.63 (1.51-1.76), respectively. Statistically significant interactions (P < 0.0001) were observed between systolic BP, diastolic BP and BMI in relation to CVD. In baseline hypertensive participants we found both obese men and women had higher risk of CVD than normal-weight persons. The multivariate-adjusted HRs(95%CI) were 1.23(1.03-1.47) and 1.20(1.02-1.40), respectively.

Conclusion

Our study suggests that the magnitude of the association between BP and CVD generally increase with increasing BMI. Hypertension should not be regarded as a less serious risk factor in obese than in lean or normal-weight persons in Chinese adults.

Does obesity modify the effect of blood pressure on the risk of cardiovascular disease? A population-based cohort study of more than one million Swedish men

BACKGROUND

Some studies have suggested that increased blood pressure has a stronger effect on the risk of cardiovascular disease (CVD) in lean persons than in obese persons, although this is not a universal finding. Given the inconsistency of this result, we tested it using a large population-based cohort data set.

METHODS AND RESULTS

Systolic and diastolic blood pressures (BPs) and body mass index were measured in 1 145 758 Swedish men born between 1951 and 1976 who were in young adulthood (median age 18.2 years). During the register-based follow-up, which lasted until the end of 2006, 65 611 new CVD events took place, including 6799 myocardial infarctions and 8827 strokes. Hazard ratios (HRs) per 1-SD increase in systolic and diastolic BP were computed within established body mass index categories (underweight, normal, overweight, or obese) with Cox proportional hazards models. The strongest associations of diastolic BP with CVD (HR 1.18), myocardial infarction (HR 1.22), and stroke (HR 1.13) were observed in the obese category. For systolic BP, the strongest associations were observed in the obese category with CVD (HR 1.16) and stroke (HR 1.29) but in the overweight category with myocardial infarction (HR 1.19). We observed statistically significant interactions (P<0.0001) with body mass index for diastolic BP in relation to CVD and for systolic BP in relation to CVD and stroke.

CONCLUSIONS

In contrast to the findings of previous studies, we observed a general increase in the magnitude of the association between blood pressure and subsequent CVD with increasing body mass index. Hypertension should not be regarded as a less serious risk factor in obese than in lean or normal-weight persons.

Meta-analysis of the effect of excluding early deaths on the estimated relationship between body mass index and mortality

OBJECTIVES

Prospective cohort studies typically observe U- or J-shaped relationships between body mass index (BMI) (kg/m2) and mortality. However, some studies suggest that the elevated mortality at lower BMIs is due to confounding by pre-existing occult disease and recommend eliminating subjects who die during the first several (k) years of follow-up. This meta-analysis tests the effects of such early death exclusion on the BMI-mortality association.

RESEARCH METHODS AND PROCEDURES

Studies identified from MEDLINE, review articles, ancestry analyses, and the "invisible college."

INCLUDED STUDIES

1) measured relative body weight at baseline; 2) included at least 1000 subjects; 3) reported results with and without early-death exclusion, or relevant data; and 4) did not study exclusively diseased populations. Blank tables were mailed to 131 investigators covering 59 databases. Completed tables (n = 16 databases), electronic raw data (n = 7 databases), and original articles (n = 6 databases) provided final data. Meta-analytic regressions compared the BMI-mortality association with and without early death exclusion. The sample included 29 studies and 1,954,345 subjects.

RESULTS

The effect of eliminating early deaths was statistically significant but minuscule in magnitude. Implementation of early death exclusion was estimated to shift the BMI associated with minimum mortality only 0.4 units for men and 0.6 units for women at age 50. Even at a BMI 16, the estimated relative risk (compared to BMI 25) decreased only 0.008 units for men and 0.076 units for women at age 50.

DISCUSSION

Results indicate that either pre-existing disease does not confound the BMI-mortality association or eliminating early deaths is inefficient for reducing that confounding.

Body weight, pre-existing disease, and all-cause mortality in a cohort of male employees in the German construction industry

The impact of body weight on all-cause mortality is subject to ongoing debate. We assessed the relation between body mass index (BMI) and all-cause mortality in a cohort of 8043 male employees in the German construction industry who underwent detailed occupational health examinations at ages 25-64 and who were followed for all cause mortality over an average period of 4.5 years. Overall, there was a negative, graded relation between BMI and all-cause mortality, which persisted after controlling for multiple covariates including age and cigarette smoking, and after excluding the initial two years of follow-up. There was a strong positive cross-sectional relationship between BMI and a medical diagnosis of diabetes, hypertension, and ischemic heart disease at the baseline examination. While BMI showed a strong negative relation with all-cause mortality among men with such diseases, the association was much weaker and non-monotonic for mean free of these diseases. Our results underline the importance of preexisting diseases for the prognostic value of body weight.

Body mass index and cardiovascular mortality at different levels of blood pressure: a prospective study of Norwegian men and women

STUDY OBJECTIVE

The study investigated the joint effect of body mass index and systolic blood pressure on cardiovascular and total mortality.

DESIGN

This was a prospective cohort study. The main outcome measures were age adjusted mortality and relative risks estimated from survival models.

SETTING

The population of the city of Bergen, Norway.

PARTICIPANTS

Subjects were 21,145 men and 30,330 women aged 30-79 years at the time of examination in 1963.

MAIN RESULTS

Both cause specific and all cause mortality increased with systolic blood pressure within each category of body mass index. Stroke mortality was not significantly associated with body mass index when adjusted for systolic blood pressure in either age group of men or women. Coronary heart disease mortality increased on average 30% per 5 kg/m2 increase in body mass index in men and women aged 30-59 years at baseline. Adjusted for systolic blood pressure, the relative risks were reduced to 1.20 (95% confidence interval (CI) 1.12, 1.29) in men and 1.10 (95% CI 1.03, 1.18) in women. They were similar at each level of systolic blood pressure. For coronary heart disease mortality in men and women aged 60-79 years at measurement a negative interaction between body mass index and systolic blood pressure was suggested in the first five years. Excluding the first five years, adjusted relative risks per 5 kg/m2, were 1.05 (95% CI 0.96, 1.15) in men and 1.11 (95% CI 1.04, 1.17) in women in the older age group. There was an upturn in cardiovascular mortality at low levels of body mass index in both age groups of women, but not in men.

CONCLUSIONS

Hypertension is an important risk factor for cardiovascular and all cause mortality even in the obese. Body mass index is generally a weak predictor of cardiovascular mortality in this population. It is a stronger risk factor of coronary death in men when measured at a younger age. Thin people with hypertension are not at particularly high risk of death from coronary heart disease compared with their obese counterparts, except possibly in the first few years after measurement in the elderly. Being underweight is associated with increased risk of death from all cardiovascular causes in women, but not in men.

Higher risk of cardiovascular mortality among lean hypertensive individuals in Tecumseh, Michigan

BACKGROUND

A cohort of 2181 men and women, aged 40 to 79 years, without evidence of coronary heart disease or cancer at entry to the Tecumseh Study was evaluated.

METHODS AND RESULTS

Subjects were defined as lean if their Metropolitan Life Insurance table relative weight was < 110 (n = 584) and as obese if their relative weight was > or = 120 (n = 1024). There were 688 subjects with hypertension at study entry (systolic blood pressure > or = 160, diastolic blood pressure > or = 95, or treated). The 29-year relative risk (RR) of mortality from ischemic heart disease (IHD) or cardiovascular disease (CVD) associated with systolic blood pressure level was significant for both lean and obese subjects. Among hypertensive subjects, the RR of fatal IHD for lean versus obese hypertensive subjects was 1.87 (95% confidence interval, 1.21 to 2.88) and the RR of fatal CVD was 1.56 (95% confidence interval, 1.10 to 2.20) using a Cox proportional-hazards model to adjust for the independent effects of age and traditional CVD risk factors. The findings are consistent with other studies in men showing lean hypertensive subjects to be at greater risk of IHD or CVD mortality than obese hypertensive subjects. A similar finding is now observed in women.

CONCLUSIONS

Associations do not prove causality or dictate management. Nevertheless, the unexplained higher mortality in lean versus obese hypertensive subjects has now been reported with sufficient frequency to suggest that the association is real (if unexplained). Determining the reasons for this association may improve targeted prevention and treatment strategies.

Why do lean hypertensives have higher mortality rates than other hypertensives? Findings of the Hypertension Detection and Follow-up Program

Specific causes of death were analyzed for 10,908 participants in the Hypertension Detection and Follow-up Program, to explore possible explanations for the observed excess 8.3-year mortality from all causes in hypertensives with low body mass. Although the cardiovascular mortality rate among men in the lowest decile of body mass (body mass index 21.96 or less) was 50% higher than that of men in the median class (body mass index 26.4-28.8), death rate for noncardiovascular deaths was more than 2 1/2 times higher in men with lean versus median body mass. The pattern was similar among women. Among noncardiovascular causes, striking differences in mortality rates between lean hypertensives and those of average body mass were observed for cirrhotic death (relative risk of 12+ in men and 11+ in women), for nonmalignant respiratory disease in men (relative risk of 7+), for violent death (both sexes), and for malignant neoplasms in men. Prevalence of smoking was almost twice as high in the lowest compared with the median body mass group; among the lean, excess deaths, particularly noncardiovascular deaths, were concentrated among smokers. Thus, male smokers in the lowest decile of body mass constituted only 3% of the study population, but contributed 8% of all deaths, 11% of all noncardiovascular deaths, and 22% of all cirrhotic deaths. A larger proportion of deaths occurred early in follow-up in the lean versus other hypertensives, suggesting occult disease among the lean at baseline. There was no evidence that more severe or treatment-resistant hypertension was present in or could explain excess mortality among the hypertensives with low body mass. The inference from the findings is not that overweight is protective for hypertensives nor that excess risk is due to leanness per se. Rather, a reasonable hypothesis, particularly from findings on specific causes of death, is that excess mortality in lean hypertensives is due to deleterious lifestyles, particularly smoking and excess alcohol intake, contributing to both leanness and risk of death.