During the past 200 years, most countries in the world have experienced a great increase in life expectancy. The timing of the onset of this decrease in mortality and corresponding increase in life expectance has vastly differed between different countries, and this is true for the pace of the development as well. Some countries have still not achieved the life expectancy experienced by the most developed countries already 100 years ago or even earlier. Some countries have even experienced a backlash in the form of declining life expectancy in the 1990s due to, for instance, unemployment and alcohol consumption in some eastern European countries, and the HIV/AIDS epidemic in some African countries. Nevertheless, the general picture of improvement remains massively impressive, and in Sweden life expectancy has increased continuously for more than 200 years. The secular mortality decline may be explained by a multitude of causes rather than one single cause. These causes may be categorised in different ways and from varying perspectives. Some causal effects (exposure leading to disease) are direct or short-term effects, others are long-term effects. The causes do not only include direct, period effects on mortality and survival such as the immediate effects of outbreaks of infectious diseases, the presence of endemic infections, as well as current hygiene, income, nutrition, housing and health care conditions. The causes also include long-term, sometimes very long-term, effects. The latter group of longterm causal mechanisms by which risk factors and protective factors affect health and disease many years later are often referred to as cohort effects, because different