A person who is born in the summer has less life expectancy than a person born in the winter. This is one of the main conclusions drawn from a study conducted by professors and researchers Jose M. Pavía and Josep Lledó, from the Department of Applied Economics of the Universitat de València. Furthermore, the research also studies the impact that correctly calculating life expectancies and the probabilities of death and survival will have for insurance companies and pension systems.
The study is entitled “Estimation of the combined effects of ageing and seasonality on mortality risk: An application to Spain” and has been published in one of the most prestigious journals in the world, the Journal of the Royal Statistical Society.
Researchers reach the conclusion that a person born in the summer has approximately three months less life expectancy than a person born in the winter, after analysing more than 180 million demographic events and studying the probabilities of dying or surviving for each age and quarter, taking into account the quarter of the year in which each person was born. This is because people who have birthdays in the winter have in common that their three previous quarters are less tough than for people who have birthdays any other quarter. This effect is similar both in men and women. Therefore, the probability of dying does not only depend on age, but also on the quarter of the year in which they were born.
Another conclusion drawn is connected to the individual’s age. In general, for a specific age, the closer the next birthday is, the higher the incidence of mortality. This fact has exceptions, such as in teenage years and especially for newborns. In this last group, improvements in medicine have significantly decrease infant mortality (in the first year of life). However, although it has decreased, the study reveals that the probability of dying in the first hours and days is still significant. For example, the probability of dying in Spain in the first quarter of a person’s life is similar to that of a man aged 65 or a woman aged 70.
Thus, according to researchers, “life expectancies and the probability of dying/surviving do not only depend on the age of the person, but also the time of year when they have their birthdays, which has implications, for example, in managing pension systems and for insurance companies.”
Winter is, for a majority of age groups, the season when there is greater mortality, tied especially to weather conditions. The higher the age, the greater the intensity of winter on mortality. This fact affects both men and women. The only noticeable differences between genders are for men aged 20 to 30, where the intensity of mortality is higher in summer, tied mainly to increased risky behaviours of young men during holidays.
The professors, who research the field of statistics and quantitative methods, have analysed a four-year period (2005-2008) of a real database comprised by microdata from the population of Spain, provided by the National Statistics Institute (INE), which included births, deaths and migrants registered in the country during those years. Furthermore, they have developed new life tables and quarterly tables.
As they say in the study, “the methodology performed in the study makes it possible to build, without requiring complex and expensive calculations, indicators of mortality (and particularly mortality tables) with intervals of less than a year”. Pavía and Lledó explain that “addressing this issue offers new opportunities to improve the management of pensions, public planning and insurance plans, with possible repercussions in the public pensions systems and the competitivity and balances of insurance companies, where the calculations, to date, had been done with annual intervals”.