Dr Aspin has an extensive record of research achievement and research management in Māori and indigenous public health. His research has focussed on issues related to the Maori health and disability workforce, as well as indigenous sexuality and the resilience of indigenous communities.

He was the lead New Zealand investigator on a collaborative project with Australia and Canada that investigated the impact of HIV on indigenous communities in the three countries, and examined the role of resilience in responding to HIV.

As a founding member of the International Indigenous Working Group on HIV and AIDS, he has been at the forefront of international efforts to address the impact of HIV on Māori and other indigenous peoples.

He has extensive governance experience and has served on a number of boards including the Health Research Council of New Zealand and Te Puawai Tapu. He held the inaugural position of Executive Research Officer at Ngā Pae o te Maramatanga, New Zealand's centre of Maori research excellence and played a key role in setting up the infrastructure of the centre. He was the Founding Editor of AlterNative, an international peer-reviewed journal of indigenous scholarship.

Dr Aspin's work focuses strongly on disparities. He is committed to addressing health and social inequities in Aotearoa where his work is designed to contribute to enhanced health and social outcomes for Māori in particular and other marginalised populations more broadly.