MPH Dissertation knowledge exchange
MPH Dissertation knowledge exchange
The role of antioxidant supplements in moderating the association between air pollution and hypertension
Air pollution is a risk factor for many health problems and its link to hypertension may be moderated by antioxidant supplements. In her 2017 MPH dissertation study, Wenqi Shen investigated the association between residential air pollutants and hypertension among middle-aged adults in the UK, with a focus on the potential moderating role of antioxidant supplements. She used secondary data from the UK Biobank Cohort Study of 502,640 adults aged 37-73 years old. Residential air pollutants - nitrogen oxides (NO2 and NOx), and particular matter (PM) with diameters of less than 2.5 µm (PM2.5) and less than 10 µm (PM10) - were included in the analyses. Multivariate logistic regression analyses with adjustment for confounding variables were used to investigate the associations between exposure to residential air pollution and hypertension. Some 24% of respondents had hypertension.
Multivariate analyses showed that, after dividing air pollutants into tertiles, the odds ratios of hypertension were: 3% and 4% respectively in the third tertile of exposure to NO2 (OR: 1.03; 95% CI: 1.01-1.06; p=0.015) and NOx (OR: 1.04; 95% CI: 1.02-1.07; p=0.002) compared to the first tertile. The odds ratios of hypertension were also 3% and 2% respectively higher in the third tertile of exposure to PM10 (OR: 1.03; 95% CI: 1.01-1.06; p=0.014) and PM2.5 (OR=1.02; 95% CI: 1.00-1.05; p=0.077). Interaction tests between air pollutants and hypertension by antioxidant supplements intake found significant result in NO2. Subgroup analyses showed that those who did not take antioxidant supplements in the second tertile for NO2 exposure were 9% more likely to have hypertension (OR: 1.09; 95% CI: 1.03-1.17; p=0.006), while no statistically significant results were found in those who took antioxidant supplements (p>0.05). Long-term exposure to residential air pollution was associated with hypertension. Taking antioxidant supplements may mitigate the adverse effect of NO2 on hypertension. Further studies are needed to confirm the modifying effect of antioxidant supplements.
Is daily driving time associated with harmful lifestyle behaviours? A population based cross-sectional study
Engaging in sedentary behaviour has been linked with a range of adverse health outcomes in adults. Car use has been specifically associated with obesity, which is a marker for poor health. Studies suggest that driving may be linked to other risky lifestyle behaviours such as inadequate sleep, poor diet and smoking, which may indirectly impact health but these associations are still inadequately understood. Alison Mackay’s 2017 UK Biobank MPH study aimed to examine whether time spent driving was associated with engaging in unhealthy lifestyle behaviours including physical inactivity, exceeding recommended intake of energy, inadequate fruit and vegetable intake, smoking, alcohol consumption and inadequate sleep, and body mass index. The total time spent driving/day and engagement in lifestyle behaviours was ascertained from a sample of middle aged drivers (n=386,493). Participants were categorised into those driving for <1 hour/day, 1 hour/day, 2 hours/day and ≥3 hours/day. Health behaviours were dichotomised into appropriate categories of low and high-risk based on public health guidelines. Initial test for trend statistics were used to analyse whether time spent driving was associated with engaging in high-risk lifestyle behaviours. Logistic regression models were then used to examine the association between drive-time categories and these behaviours. Models were adjusted for socio-demographic variables and other lifestyle behaviours which may have potential to confound or mediate the association. The Hosmer-Lemeshow test was used to determine the model fit. A significance level of 5% was reported for all statistics.
Unadjusted statistical trend analysis found drive-time to be statistically significantly associated with being overweight or obese, smoking, higher alcohol consumption, inadequate fruit and vegetable intake, inadequate physical activity, short sleep, (p<0.001). Adjusted logistic regression found that, independent of possible confounding and mediating variables, drive-time had a statistically significant (<0.05) independent dose-response relationship with being overweight or obese (1hr:OR 1.25, CI 1.21-1.29; 2hrs: OR 1.44, CI 1.39-1.50; ≥3hrs: OR 1.76,CI 1.66-1.87, [ref<1hr]), being a current smoker (1hr: OR 1.15, CI 1.09-1.21; 2hrs: OR 1.27, CI 1.19-1.36; 3hrs: OR 1.48, CI 1.35-1.62 [ref<1hr]) or getting inadequate sleep (1hr: OR 1.16, CI 1.13-1.20; 2hr: OR 1.44, CI 1.38-1.50; 3hr: OR 1.70, CI 1.61-1.80 [ref<1hr])). Although a dose-response relationship did not exist, driving for ≥1 hour/daywas associated with inadequate fruit and vegetable intake with the highest odds in those driving the most (1hr: OR 1.16, CI 1.11-1.20; 2hrs: OR 1.11, CI 1.06-1.17; 3hrs: OR 1.24, CI 1.16-1.33 [ref<1hr]). Driving for ≥2 hours/day was associated with inadequate physical activity however this relationship was not dose-dependent (2hrs: OR 1.09, CI 1.05-1.13; ≥3hrs: OR 1.06, CI 1.00-1.12; [ref<1hr]) and those driving for 1 hour/day had marginally higher odds of doing more PA (OR 0.97, CI 0.94-1.00). Conversely, driving ≥3 hours/day was borderline significantly associated with drinking <14 units of alcohol/week (OR 0.93, CI 0.86-1.00 [ref<1hr]). Only those driving for 1 hour/day had a 3% higher odds of exceeding recommended daily energy levels (OR 1.03, CI 1.01–1.06). No association was found across longer periods of driving.
Time spent driving was strongly associated with increased likelihood of being overweight or obese. Results suggest that driving for ≥2/day is associated with a range of unhealthy lifestyle behaviours independent of a number of potential confounders or mediators and as such may be detrimental to the health of middle-aged adults. These findings suggest that population interventions to reduce time spent driving could not only support a reduction in BMI but may have additional benefits on sleep, smoking, physical activity and fruit and vegetable intake. Results support the design of health interventions that target individuals who spend large periods of time driving each day.
The association between marital status and risk of hypertension: A systematic review and meta-analysis
Hypertension is one of the most common non-communicable diseases and it is also a risk factor for cardiovascular disease. Marital status has an important role in hypertension including: marital stress effect on blood pressure and long-term blood pressure change of widowhood. In western countries, marital status is already confirmed as a cardiovascular risk factor. However, until now, there has been no research specifically comparing the effects of marital status on risk of hypertension and Wen Luo’s 2017 MPH dissertation aimed to evaluate the association between marital status and hypertension risk using systematic review of literature. Five databases were searched, studies were screened, and 31 studies included in the meta-analysis. Meta-analysis results showed that single males, married females, and divorced and widowed people might have a higher risk of hypertension.