Ambient particulate matter and biomass burning: an ecological time series study of respiratory and cardiovascular hospital visits in northern Thailand.

BACKGROUND: Exposure to particulate matter (PM) emitted from biomass burning is an increasing concern, particularly in Southeast Asia. It is not yet clear how the source of PM influences the risk of an adverse health outcome. The objective of this study was to quantify and compare health risks of PM from biomass burning and non-biomass burning sources in northern Thailand. METHODS: We collected ambient air pollutant data (PM with a diameter of < 10 µm [PM10], PM2.5, Carbon Monoxide [CO], Ozone [O3], and Nitrogen Dioxide [NO2]) from ground-based monitors and daily outpatient hospital visits in Thailand during 2014-2017. Outpatient data included chronic lower respiratory disease (CLRD), ischaemic heart disease (IHD), and cerebrovascular disease (CBVD). We performed an ecological time series analysis to evaluate the association between daily air pollutants and outpatient visits. We used the 90th and 95th percentiles of PM10 concentrations to determine days of exposure to PM predominantly from biomass burning. RESULTS: There was significant intra annual variation in PM10 levels, with the highest concentrations occurring during March, coinciding with peak biomass burning. Incidence Rate Ratios (IRRs) between daily PM10 and outpatient visits were elevated most on the same day as exposure for CLRD = 1.020 (95% CI: 1.012 to 1.028) and CBVD = 1.020 (95% CI: 1.004 to 1.035), with no association with IHD = 0.994 (95% CI: 0.974 to 1.014). Adjusting for CO tended to increase effect estimates. We did not find evidence of an exposure response relationship with levels of PM10 on days of biomass burning. CONCLUSIONS: We found same-day exposures of PM10 to be associated with certain respiratory and cardiovascular outpatient visits. We advise implementing measures to reduce population exposures to PM wherever possible, and to improve understanding of health effects associated with burning specific types of biomass in areas where such large-scale activities occur.

Diet modification in lowering plasma cholesterol levels. A randomised trial of three types of intervention.

OBJECTIVE: To compare the efficacy of three types of diet and lifestyle interventions for lowering plasma lipid levels. DESIGN: Randomised parallel-group trial. SUBJECTS AND SETTING: Adults with plasma cholesterol levels of 5.5-8.0 mmol/L attending two Sydney community health screening clinics were asked to participate: 179 agreed and 131 completed the study. INTERVENTIONS: A pamphlet with brief advice; group dietary counselling; or individual counselling. Counselling included three sessions with a dietitian/nutritionist over six months. MAIN OUTCOME MEASURES: Plasma total cholesterol levels measured by Reflotron analyser; fasting serum lipid levels measured by standard laboratory methods; and calculated low-density lipoprotein cholesterol levels. RESULTS: Significantly lower plasma total cholesterol levels (Reflotron) were observed at two months and at six months with each of the three interventions. Additionally, both types of dietitian-based counselling resulted in small but significant decreases in plasma low-density lipoprotein cholesterol levels at six months in a subset of subjects. CONCLUSION: Although there were no statistically significant differences in efficacy between the three types of intervention, dietitians have a role to play in setting up such counselling programs.

Comparative and combined efficacy of doxazosin and enalapril in hypertensive patients.

Twenty patients with essential hypertension were randomised to a 7-week period of dose titration with doxazosin, 1-8mg/day or enalapril, 5-20mg/day. In a further 7-week period the dosage level reached with the initial drug was halved, and titration with the second agent was carried out. Blood pressure responses at the end of each treatment period were assessed by clinic measurements made 24 hours post-dose. In the first treatment period, enalapril (mean dose 19mg/day) reduced serum free ACE activity by 40% and had a greater effect than doxazosin (mean dose 5.2mg/day) on clinic supine blood pressure (systolic and diastolic). In the second period, the addition of enalapril to doxazosin was associated with a significant fall in clinic standing blood pressure (systolic and diastolic), despite the doxazosin dose reduction and consequent decrease in median plasma doxazosin concentration (from 10.6 to 5.2ng/ml). Alternatively, when doxazosin was added to enalapril, free ACE activity remained 40% decreased despite enalapril dose reduction, and blood pressure was not further affected. Plasma renin activity was increased by enalapril. No changes were observed in plasma aldosterone or lipid concentrations with either drug. The combination of doxazosin and enalapril was well tolerated and lowered blood pressure overall. Judged by clinic measurements 24 hours post-dose, most of the antihypertensive effect was attributable to the enalapril component. However, ambulatory blood pressure monitoring 0-12 hours post-dose in a subset of patients suggested a contribution of doxazosin earlier in the dose interval.

Humoral determinants of Na+ excretion after intravenous NaCl loading in normal volunteers.

1. Twelve healthy volunteers maintained on a 100 mmol/day Na+ diet, were given an intravenous infusion of 2L saline (0.9%) between 10.00 h on 2 study days at least 1 week apart. Urine collections (90 min) were made from 08.30 to 16.00 h. Either carbidopa 100 mg or indomethacin 50 mg was given orally at 07.45 h on one study day and placebo was given on the other (in random order). 2. On the placebo day, saline infusion caused significant decreases in plasma albumin concentration, plasma renin activity (PRA), plasma aldosterone concentration and urinary aldosterone excretion, with 2 to 3-fold increases in plasma atrial natriuretic peptide (ANP) concentration and urinary dopamine: noradrenaline ratio (DA:NA), whereas mean urinary kallikrein and prostaglandin E2 (PGE2) excretion rates were unchanged. Carbidopa decreased urinary DA:NA and indomethacin decreased urinary PGE2 excretion, compared with the placebo day. Excretion of sodium (Na+) decreased below baseline in two out of six carbidopa-treated subjects and in three out of six indomethacin-treated subjects, but showed little or no change in the remainder. 3. These preliminary observations suggest that some subjects in the early phase of natriuresis after an intravenous Na+ load can be identified as having prostaglandin-dependent or dopamine-dependent mechanisms for Na+ excretion.

The effects of sulindac and diclofenac in essential hypertension controlled by treatment with a beta blocker and/or diuretic.

A placebo-controlled, double blind crossover study of the non-steroidal anti-inflammatory drugs (NSAIDs) sulindac and diclofenac was conducted in 16 patients with essential hypertension that was controlled by treatment with a beta blocker, a diuretic or co-administration of both. In 4 cases, another antihypertensive agent (prazosin or verapamil) was also co-administered. In every patient, plasma creatinine concentration was less than 0.14 mmol/l (normal range 0.07-0.12 mmol/l). Sulindac and diclofenac were each given for 7 weeks. Diclofenac caused a decrease of borderline significance in plasma aldosterone concentration. Neither NSAID altered the mean values for systolic or diastolic blood pressure, body weight, plasma electrolyte concentrations, urate clearance, creatinine clearance or plasma renin activity. However, rises in plasma creatinine concentration and falls in creatinine clearance occurred during NSAID therapy in three individual subjects. No significant differences were observed in this study between the effects on renal function or blood pressure of sulindac and diclofenac, both of which appear not to interfere with the antihypertensive actions of beta blockers and diuretics.

Timing of blood pressure measurements in determining anomalies in duration of effect of an antihypertensive drug: assessment of isradipine.

Analysis of an antihypertensive drug trial, which involved measurements of blood pressure (BP) during visits to the clinic at a set time of day, showed that the initial dosage titration procedure had been inadequate in some patients. Plasma drug concentration-time curves and corresponding BP values suggested that control of BP was closely related to plasma drug concentration and that the duration of drug effect was shorter than the dosage interval of 12 h. This interpretation was supported by measurements of BP and drug concentrations taken at steady state, before and 2 h after taking the drug. Measurements of ambulatory BP revealed that some patients whose doses had been titrated at peak plasma drug concentrations had high BP at the time of trough plasma drug concentrations, whereas some of those titrated at trough times were hypotensive at peak times. Adjustment of antihypertensive therapy should entail observations of BP at times coincident with both peak and trough concentrations of the drug concerned, and can be facilitated by ambulatory BP monitoring.