Churches will continue to attract older congregations as increasing life expectancy encourages people to put off involvement in religion, according to new research.

The study, by Dr Elissaios Papyrakis at the University of East Anglia and Dr Geethanjali Selvaretnam from the University of St Andrews in the UK, suggests that religious organisations need to do more to highlight the social and spiritual benefits of participation in religion in present day life if they are to increase congregation sizes and attract people of all ages, particularly young people.

Published online in the International Journal of Social Economics, the research looks at the impact of life expectancy on religiosity - the extent of religious dedication and expression - and the decisions made by individuals about when to become involved in religion. The study analyses religiosity using a cost-benefit economic model, where decisions at each point in time depend on social and spiritual benefits attached to religious adherence, the probability of entering heaven in the afterlife, as well as the costs of formal religion in terms of time allocated to religious activities.

Dr Papyrakis and Dr Selvaretnam explain not only the downward trend in church attendance, but also the increase in the proportion of older people in congregations.

In recent years, religious establishments have been concerned about decreasing religious expression and participation in most parts of the world, particularly in developed economies, with many churches seeing older and dwindling congregations. In the UK, church attendance has been consistently on the decline in the past 50 years. However, in many sub-Saharan African and Latin American nations, for example, religious adherence remains strong.

Previous studies have attempted to attribute these differing patterns in religiosity to several socio-economic variables, including the level of economic development, government regulation of the 'religion market' and suppression of religion. This new research, entitled The Greying Church: the Impact of Life Expectancy on Religiosity, explores the role of life expectancy in explaining differences in religious expression around the world.

"The findings have important policy implications for what churches want to do and how they attract members," explained Dr Papyrakis, of the School of International Development at UEA. "Many religions and societies link to some degree the cumulative amount of religious effort to benefits in the afterlife. We show that higher life expectancy discounts expected benefits in the afterlife and is therefore likely to lead to postponement of religiosity, without necessarily jeopardising benefits in the afterlife.

"For this reason, religious organisations should be prepared to accept and attract a 'greying church', with membership skewed towards the older generation, particularly in countries which have high life expectancy or expect significant increases in life expectancy, for example due to improvements in medical care or declines in critical infection rates."

Dr Papyrakis added: "To increase overall attendance, religious establishments should aim to reduce any discomfort of entry to religious newcomers, both old and young. This may involve making information about the organisation easily accessible to them and helping new-comers to follow religious activities without feeling lost or uncomfortable.

"In light of rising life expectancy, it is important to emphasise socio-economic and spiritual benefits that can be enjoyed during one's lifetime on earth, for example expanding a person's social circle, communal activities, spiritual fulfilment, support and guidance, rather than uncertain rewards in the afterlife. These benefits can counterbalance the negative impact of life expectancy on religiosity – which in effect reduces concern about life after death – and therefore encourage religious involvement."

Religions that largely delink salvation/damnation to the timing and amount of religious effort will particularly need to resort to such means to boost membership numbers. In most religions, the perceived probability of entering heaven or hell depends to a certain degree on the individual's lifetime behaviour. The degree of this varies across religions, being relatively high in Buddhism and Catholicism, but lower in Protestantism. In Calvinism, in particular, salvation/damnation is largely seen as predestined.

In poorer countries where life expectancy remains low, a larger share of the population, both young and old, is concerned about what happens after death, which naturally encourages religious participation.