Arsenic exposure from drinking water and mortality from cardiovascular disease in Bangladesh: prospective cohort study

Abstract

Objective: To evaluate the association between arsenic exposure and mortality from cardiovascular disease and to assess whether cigarette smoking influences the association.

Design: Prospective cohort study with arsenic exposure measured in drinking water from wells and urine.

Setting: General population in Araihazar, Bangladesh.

Participants: 11,746 men and women who provided urine samples in 2000 and were followed up for an average of 6.6 years.

Main outcome measure: Death from cardiovascular disease.

Results: 198 people died from diseases of circulatory system, accounting for 43% of total mortality in the population. The mortality rate for cardiovascular disease was 214.3 per 100,000 person years in people drinking water containing <12.0 µg/L arsenic, compared with 271.1 per 100,000 person years in people drinking water with ≥ 12.0 µg/L arsenic. There was a dose-response relation between exposure to arsenic in well water assessed at baseline and mortality from ischaemic heart disease and other heart disease; the hazard ratios in increasing quarters of arsenic concentration in well water (0.1-12.0, 12.1-62.0, 62.1-148.0, and 148.1-864.0 µg/L) were 1.00 (reference), 1.22 (0.65 to 2.32), 1.35 (0.71 to 2.57), and 1.92 (1.07 to 3.43) (P = 0.0019 for trend), respectively, after adjustment for potential confounders including age, sex, smoking status, educational attainment, body mass index (BMI), and changes in urinary arsenic concentration since baseline. Similar associations were observed when baseline total urinary arsenic was used as the exposure variable and for mortality from ischaemic heart disease specifically. The data indicate a significant synergistic interaction between arsenic exposure and cigarette smoking in mortality from ischaemic heart disease and other heart disease. In particular, the hazard ratio for the joint effect of a moderate level of arsenic exposure (middle third of well arsenic concentration 25.3-114.0 µg/L, mean 63.5 µg/L) and cigarette smoking on mortality from heart disease was greater than the sum of the hazard ratios associated with their individual effect (relative excess risk for interaction 1.56, 0.05 to 3.14; P = 0.010).

Conclusions: Exposure to arsenic in drinking water is adversely associated with mortality from heart disease, especially among smokers.

Fig 1 Equations for time weighted arsenic concentration and population attributable proportion of mortality from cardiovascular disease

Fig 2 Joint effect of cigarette smoking and concentrations of well arsenic at baseline on mortality from ischaemic heart disease and other heart disease. Hazard ratios adjusted for sex and baseline age (years), BMI, education, and changes in urinary creatinine adjusted arsenic (µg/g of creatinine) between visits

Fig 3 Multivariate adjusted (education, age, BMI, changes in urinary arsenic over time) survival curves for ischaemic heart disease and other heart disease by baseline concentrations of well arsenic (low, medium, and high), sex, and baseline smoking status. Drop in survival curves around year 8 was because all participants who were alive at the end of third (final) follow-up visit were censored at date of that visit