Heart doi:10.1136/heartjnl-2014-305877
  • Editorial

Less clarity as the fog begins to lift

  1. David E Newby
  1. Royal Infirmary of Edinburgh, Edinburgh, UK
  1. Correspondence to Dr Anoop Shah, BHF/University Centre for Cardiovascular Science, Chancellor's Building, Royal Infirmary, Little France, Edinburgh EH16 4SB, UK; anoop.shah{at}

Epidemiological and clinical evidence accumulated over the last six decades has established a long-standing and close temporal relationship of air pollution with adverse health effects: from the extreme episodes of the Meuse Valley fog in 1930 and the London fog incident in 1952 to recent studies implicating ambient air pollution as a major perpetrator of adverse health effects. Globally, ambient particulate pollution is responsible for an estimated 3.2 million deaths worldwide, primarily driven by cardiovascular events.1

Several recent studies, using time-series and case-crossover study designs, have investigated the association of ambient air pollution and adverse cardiovascular events. Short-term exposure studies are more sensitive to daily fluctuations in outcomes and exposures (in this case pollutants), and allow greater control of potential temporal confounders providing a more accurate insight into the real impact of pollution on adverse health events. However, there still remains considerable variation in overall effect estimates reported in the literature due to various factors including heterogeneity in the underlying population studied, accurate measurement of the pollutants, analytical variation in terms of controlling for confounding and choice of lag (time interval between exposure and outcome) used for each pollutant.

Coronary heart disease, cerebrovascular disease and heart failure are the three most common causes of morbidity or mortality. In this issue of Heart, Milojevic and colleagues present a more contemporary analysis from three nationwide databases in the UK, on …