Are early life factors responsible for international differences in adult blood pressure? An ecological study

Diverse associations between adiposity and blood pressure among 80,000 multi-ethnic Chinese adults

BACKGROUND

Adiposity is widely recognized as one of the risk factors for high blood pressure (BP) and increasing adiposity is associated with elevated BP. However, which measures of adiposity could be most strongly associated with BP in multi-ethnic population remains uncertain, giving rise to implications that population-based adiposity measures could be necessary.

METHODS

80,000 multi-ethnic adults recruited from 5 provinces across Southwest China during 2018 ~ 2019 were studied. Multiple linear regression was applied to investigate the associations of systolic blood pressure (SBP) with: (1) two measures of general adiposity, body mass index (BMI) and height-adjusted weight; and (2) three measures of central adiposity, waist circumference (WC), hip circumference (HC) and waist hip ratio (WHR).

RESULTS

Two distinct population-specific patterns were identified, as "BMI to SBP" and "WC to SBP". 90% of the participants fall into "BMI to SBP" pattern, in which the associations of SBP with BMI were independent of WC, and SBP-WC associations were considerably decreased by adjustment for BMI. And in this pattern, 10 kg/m² greater BMI was associated with 11.9 mm Hg higher SBP on average. As for the rest population (Han males in Yunnan and Tibetans in Lhasa), they are suited for "WC to SBP" pattern, 10 cm wider WC was associated with 3.4 mm Hg higher SBP.

CONCLUSION

Our results indicated that when selecting proper predictors for BP, population-specific adiposity measures are needed, considering ethnicity, sex and residing regions. A better understanding of adiposity and BP may better contribute to the potential clinical practices and developing precision application strategies.

Adiposity and Blood Pressure in 110 000 Mexican Adults

Previous studies have reached differing conclusions about the importance of general versus central markers of adiposity to blood pressure, leading to suggestions that population-specific adiposity thresholds may be needed. We examined the relevance of adiposity to blood pressure among 111 911 men and women who, when recruited into the Mexico City Prospective Study, were aged 35 to 89 years, had no chronic disease, and were not taking antihypertensives. Linear regression was used to estimate the effects on systolic and diastolic blood pressure of 2 markers of general adiposity (body mass index and height-adjusted weight) and 4 markers of central adiposity (waist circumference, hip circumference, waist:hip ratio, and waist:height ratio), adjusted for relevant confounders. Mean (SD) adiposity levels were: body mass index (28.7±4.5 kg/m²), height-adjusted weight (70.2±11.2 kg), waist circumference (93.3±10.6 cm), hip circumference (104.0±9.0 cm), waist:hip ratio (0.90±0.06), and waist:height ratio (0.60±0.07). Associations with blood pressure were linear with no threshold levels below which lower general or central adiposity was not associated with lower blood pressure. On average, each 1 SD higher measured adiposity marker was associated with a 3 mm Hg higher systolic blood pressure and 2 mm Hg higher diastolic blood pressure (SEs <0.1 mm Hg), but for the waist:hip ratio, associations were only approximately half as strong. General adiposity associations were independent of central adiposity, but central adiposity associations were substantially reduced by adjustment for general adiposity. Findings were similar for men and women. In Mexican adults, often overweight or obese, markers of general adiposity were stronger independent predictors of blood pressure than measured markers of central adiposity, with no threshold effects.

The effect of abnormal birth history on ambulatory blood pressure and disease progression in children with chronic kidney disease

OBJECTIVE

To examine the associations between abnormal birth history (birth weight <2500 g, gestational age <36 weeks, or small for gestational age), blood pressure (BP), and renal function among 332 participants (97 with abnormal and 235 with normal birth history) in the Chronic Kidney Disease in Children Study, a cohort of children with chronic kidney disease (CKD).

STUDY DESIGN

Casual and 24-hour ambulatory BP were obtained. Glomerular filtration rate (GFR) was determined by iohexol disappearance. Confounders (birth and maternal characteristics, socioeconomic status) were used to generate predicted probabilities of abnormal birth history for propensity score matching. Weighted linear and logistic regression models with adjustment for quintiles of propensity scores and CKD diagnosis were used to assess the impact of birth history on BP and GFR.

RESULTS

Age at enrollment, percent with glomerular disease, and baseline GFR were similar between the groups. Those with abnormal birth history were more likely to be female, of Black race or Hispanic ethnicity, to have low household income, or part of a multiple birth. Unadjusted BP measurements, baseline GFR, and change in GFR did not differ significantly between the groups; no differences were seen after adjusting for confounders by propensity score matching.

CONCLUSIONS

Abnormal birth history does not appear to have exerted a significant influence on BP or GFR in this cohort of children with CKD. The absence of an observed association is likely secondary to the dominant effects of underlying CKD and its treatment.

Drawing causal inferences in epidemiologic studies of early life influences

Observational studies can describe associations between early life exposures and subsequent outcomes in human populations. It is challenging to draw causal inferences from these associations because exposures often occur many years before the outcome and are related to other early life exposures. An approach is required that combines traditional epidemiologic and statistical principles with the use of novel and sophisticated analytic methods. To minimize the bias in longitudinal studies of early origins, researchers need to do all they can to reduce losses to follow-up and to describe individuals who are lost to follow-up. To reduce the role of chance, researchers should concentrate on effect sizes and the strength of the evidence to support these effect sizes, and they should be cautious in their interpretation of subgroup analyses. More complex analytic approaches can and should be used to handle missing data and repeated measurements. Addressing the issue of confounding is not straightforward. Statistical adjustment for the confounders measured in a study may help, but a lack of attenuation does not guarantee that the association is not confounded. Ecologic studies, observational studies in populations with different confounding structures, and the follow-up of randomized trials (where these exist) can be informative. Genetic and nongenetic instrumental variable approaches (eg, Mendelian randomization) may also provide causal insights. These approaches to confounding often require the comparison of data from different populations or a combination of studies to ensure adequate power to provide robust estimates of the causal effect.

Ecological analysis of the relationship between infant mortality and cardiovascular disease mortality at ages 45-69 in the Brazilian 1935 birth cohort

BACKGROUND

International ecological studies have shown a positive association between infant mortality as a proxy for low birth weight and cardiovascular disease mortality in adult life.

METHODS

Mortality rates due to Cardiovascular Diseases (CVDMR) standardised by age in adults between 45 and 69 years of age and by place of birth (pob) and residence (res) were related to Infant Mortality Rates (IMR) in the Brazilian 1935 birth cohort.

RESULTS

Two relationship patterns were noted between IMR and CVDMR: for the Southeast, South and Centre-West group of regions (r(pob)=0.46; r(res)=0.29) and for the North and Northeast group of regions (r(pob)=0.21; r(res)=0.33). For the latter pattern, two states were identified (Rio Grande do Norte and Paraíba) as atypical areas, whose exclusion strengthened the association (r(pob)=0.73; r(res)=0.91).

CONCLUSIONS

The direction of the associations changed after the analysis by group of Brazilian regions (indirect control of socio-economic levels, coverage and quality of the information). There is a positive, although weak association between IMR and CVDMR. Attempts to control or minimise the interference of migratory movements, cohort effects and socio-economic levels represented methodological progress in ecological analyses of foetal programming in Brazil.

Hypertension and happiness across nations

In surveys of well-being, countries such as Denmark and the Netherlands emerge as particularly happy while nations like Germany and Italy report lower levels of happiness. But are these kinds of findings credible? This paper provides some evidence that the answer is yes. Using data on 16 countries, it shows that happier nations report systematically lower levels of hypertension. As well as potentially validating the differences in measured happiness across nations, this suggests that blood-pressure readings might be valuable as part of a national well-being index. A new ranking of European nations' GHQ-N6 mental health scores is also given.

Association of diarrhoea in childhood with blood pressure and coronary heart disease in older age: analyses of two UK cohort studies

BACKGROUND

There is a suggestion that acute dehydration in childhood may lead to elevated blood pressure. We examined if episodes of diarrhoea in childhood, a recognized proxy for acute dehydration, were related to measured blood pressure and coronary heart disease in older adults.

METHODS

Data were pooled from two prospective UK cohort studies (participants born 1920-39) in which episodes of diarrhoea were ascertained from health visitor records from birth until 5 years of age. Blood pressure and coronary heart disease were assessed during medical examination in men and women over 64 years of age. In total, 5203 men and women had data on diarrhoea in early life, adult blood pressure and a range of covariates; 4181 of these also had data on coronary heart disease status.

RESULTS

The prevalence of diarrhoea in infancy (3.3%) and between 1 and 5 years (1.1%) was low. There was no relation of diarrhoea from either period (age- and sex-adjusted results for diarrhoea in infancy presented here) with measured blood pressure [coefficient for systolic; 95% CI (confidence interval): 0.44; -2.88-3.76] or coronary heart disease (Odds ratio, OR; 95% CI: 0.91; 0.54-1.54) in adulthood. There was a similar lack of association when hypertension was the outcome of interest. These observations were unchanged after adjustment for a range of covariates.

CONCLUSIONS

In the largest study to date to examine the relation, there was no evidence that diarrhoea in early life had an influence on measured blood pressure, hypertension or coronary heart disease in older adults.