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An investigation of geographic blood pressure variations among men and women in britain.

Bruce, Nigel Graeme; (1991) An investigation of geographic blood pressure variations among men and women in britain. Doctoral thesis (Ph.D.), Royal Free Hospital School of Medicine. Green open access

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Abstract

The age at which blood pressure (BP) variations between different communities emerge has important implications for aetiological research and for the primary prevention of hypertension. An opportunity to investigate this question in Britain arose with the finding of marked differences in mean BP of men aged 40-59 living in the 24 towns included in the British Regional Heart Study (BRHS). The Nine Towns Study (NTS) was set up to investigate whether these geographic variations in BP also existed for women, whether they were already present in young adults, and to begin exploring the reasons for the differences. A total of 2610 men and women aged 25-29, 40-44, and 55-59 form nine of the BRHS towns were examined, the towns having been chosen to cover the full range of mean BPs identified in the BRHS. A Dinamap 1846 automated recorder was used to minimise observer variation in BP measurement. Differences in age-adjusted mean town BPs at 40-59 years were 9.0 mmHg systolic in men (ANOVA; p=0.05) and 8.6 mmHg systolic in women (NS), and 5.0 mmHg diastolic (p<0.001) in men and 4.5 mmHg diastolic in women (p<0.01). The magnitude of the differences at 25-29 years were similar, and furthermore it was found that towns with higher mean BP in middle age tended to have higher mean BP in the young adults (correlations between town mean BPs at 25-29 and at 40-59 were, for systolic: r=0.74 for men and 0.65 for women; diastolic: r=0.76 for men and 0.78 for women). Associations between mean town BP in the NTS and in the BRHS at ages 40-59 were apparent for systolic (men r=0.66 p<0.05, women r=0.55), but not for diastolic. The associations between town BPs and the town mortality rates for cardiovascular disease were much stronger, with correlations of 0.81 (p<0.01) for systolic in men, and r=0.74 (p<0.05) for systolic in women. There was no evidence that the slopes of BP rise with age differed between the towns, either when the BP values for each subject were regressed linearly on age, or when differences in rates of hypotensive medication with age were taken into account. It is concluded that the geographic BP differences seen in late middle-age are already established by age 25-29. The Dinamap was compared with a Hawksley Random Zero sphygmomanometer in three separate validation studies covering the period of the main survey, and showed acceptable repeatability. Medication effects were allowed for by adjusting the town medians assuming that treated subjects had pre-treatment BP levels that were higher than the median for their age/sex group. A study of general practice BP readings for responders and non-responders suggested that the response rate, which varied between towns and age/sex groups, would not have introduced important bias. Overall observer effects were small, but there was evidence that the difference between observers varied between towns. Room and outdoor temperature and outdoor humidity were not important factors in explaining the pattern of town BP results. The most important validation of the findings came from the associations between mean town BPs and cardiovascular mortality. This study has shown that geographic blood pressure variations in Britain are already established in men and women aged 25-29 years. These results are consistent with the findings of studies which compare populations in different countries, urban/rural comparisons, and studies of different racial groups. Preliminary work on the causes of the geographic blood pressure differences is presented, and this suggests that BMI, the Na/K ratio and alcohol consumption are the most important factors for systolic differences in men, and BMI and Na/K for systolic differences in women. However, these factors explained very little of the geographic differences in diastolic blood pressure. The results of this study indicate the potential value of research into the determinants of differing population blood pressure levels in children and adolescents, and suggest that action on obesity, the Na/K ratio and alcohol consumption would be a valuable part of a public health strategy aimed at the primary prevention of raised blood pressure.

Type: Thesis (Doctoral)
Qualification: Ph.D.
Title: An investigation of geographic blood pressure variations among men and women in britain.
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by Proquest
URI: https://discovery.ucl.ac.uk/id/eprint/10108109
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