Hypertension and Stroke: Associations with Physical Activity and BMI in Māori and Non-Māori in Advanced Age

Abstract

Background Hypertension and stroke are major public health problems in New Zealand. In 2015/16, one in six New Zealanders had self-reported hypertension and were taking antihypertensive treatment. Stroke was the third largest recorded cause of death in 2012, and the third leading cause of premature mortality in 2013. Although there are previous studies on hypertension and stroke in adults, the understanding of associations between hypertension, physical activity, BMI with stroke and mortality outcomes in the oldest old is still limited. Aim To examine the association of hypertension, physical activity, and BMI with stroke and mortality, controlling for confounders, in advanced age in Māori and non-Māori New Zealanders. Methods This study used secondary data from LiLACS NZ (Life and Living in Advanced Age: A Cohort Study in New Zealand) and the National Minimum Dataset (Hospitalisation Events). Univariate and multivariate Cox regression analyses were used to determine the association of blood pressure levels, physical activity status, BMI with stroke and mortality outcomes, adjusting for age, sex, education, NZ deprivation status (NZDep 06), smoking, comorbidities such as congestive heart failure, cardiovascular diseases and diabetes mellitus, and number of blood pressure-lowering drugs. In addition, the association of baseline TIA, stroke, TIA/stroke with all-cause mortality was also examined using multivariate Cox regression analysis. Results The SBP ≥ 180 mmHg and DBP 100-109.9 mmHg was associated with an increased 60-months risk of stroke, and TIA/stroke in non-Māori, but not in Māori. A significant positive association in Māori was observed for SBP ≥ 180 mmHg and DBP 90-99.9 mmHg with mortality, but not in non-Māori. Similar to the national mortality data, Māori had a higher risk of mortality than non-Māori after adjusting for age and sex. In Māori, the 60-months stroke risk was significantly increased by the presence of AF, but not by DM, CHF, CAD or PVD, controlling for confounders and SBP, and DBP. In non-Māori, stroke risk was not associated with AF, CHF, CAD or PVD, nor DM controlling for confounders and SBP, and DBP. In Māori, after adjusting SBP and confounders, the mortality risk was significantly increased by AF, but not by CHF, CAD or PVD, and DM. When DBP and confounders are adjusted, the mortality risk was significantly increased by AF, and CHF, but not by CAD or PVD. In non-Māori, the mortality risk was significantly increased by CHF, CAD or PVD, and DM, but not by AF after adjusting for confounders with SBP, and with DBP. However, DM was not associated when CAD or PVD were adjusted. Implications Blood pressure is the important risk factor for stroke and mortality. Management strategies for both SBP and DBP should be tested in the oldest old to estimate treatment effect.