Dunedin's world-famous longitudinal study is having babies.

Since 1972, Otago's Multidisciplinary Health and Development Study has tracked the lives of 1,037 Dunedin-born individuals, uncovering information ranging from the relationship between blood inflammation as an adult and being maltreated as a child, to the educational impacts of watching TV. It is regarded as arguably the best longitudinal study in the world.

Now, the researchers are taking the study to another level - another generation.

They are carrying out one-off, one-day assessments of the study members' children at the age of 15.

This gives the researchers an unparalleled opportunity to "look at how various issues pass through the generations".

Deputy director Associate Professor Bob Hancox explains this gives the researchers an unparalleled opportunity to "look at how various issues pass through the generations".

"For example, we know that many illnesses 'run in families'. But very little is known about how this happens, and how the physiological and lifestyle triggers might work together."

Further topics piquing the interest of researchers include lifestyle differences between today's teenagers and their parents. "What does it mean to have grown up surrounded by so much technology? Are kids really less fit and active than their parents were? How are children influenced by the way they've been parented?"

The age of 15 was identified as the optimal age for the study, as representing "a part of childhood, while being a launch pad for adulthood".

"At this age, children are still at school and living with their families without the complications of adulthood. Yet they are often able to understand and reflect on their lives quite well, and issues around mental health and well-being will probably have already emerged," Hancox says.

So far, some 40 children have been assessed, but Hancox believes it will be at least another five years before enough information is gathered to start yielding results.

"Those we've assessed so far are the children of younger parents. This in itself may generate interesting findings, but it will be years before we have comparative information from children of older parents."

Already, the design of the study is attracting attention. While the concept of the nuclear family as the dominant family structure is routinely challenged, it has rarely been possible for a broader understanding of what makes up a "family" to be properly assessed in this sort of research.

"We ask participants about their life history, shared care, who lives with them, how their household has changed, what other adults perform parenting roles. What we want to do is capture the complexity of family life during the first 15 years."

Hancox believes this approach will lead to a much greater ability to unpack how family structure relates to health and well-being outcomes for children. "The shift from nuclear families is often described in very black-and-white terms by some members of society, with a great deal of speculation and conjecture thrown in. We think we can do better than that."

Ultimately, says Hancox, the one-off assessment will provide further insights into questions of how nature and nurture work together to make us who we are.

As well as the continuing assessment of the original study members, the Dunedin unit has recently completed in-depth interviews of their parents to provide more information about the study members' family of origin. So the Next Generation Study will provide us with the opportunity to examine health and lifestyle issues across three generations. Says Hancox, "This will become an incredibly valuable resource of information indeed."