Samoa study cites genetic Parkinson’s pattern and gaps in Pacific care

By Ron Rocky Coloma

A new wave of Parkinson’s disease research in the Pacific points to both a clearer genetic signal and persistent gaps in access to care, particularly in Samoa, where specialists are scarce and diagnoses often come late.

Dr. Joseph Donnelly, a neurologist and a fellow at the Neurological Foundation VJ Chapman, said recent fieldwork in Samoa identified a strong link between early-onset Parkinson’s disease and a specific genetic variant known as PINK1, while also exposing challenges in detection and treatment in island settings.

“Parkinson’s disease recognition is often quite difficult because it tends to occur slowly over many years,” Donnelly said. “Often, it is when people who haven’t seen you in a long time see you after a couple of years and say, ‘What’s happening here?’”

During a five-week clinical and research trip, Donnelly and his team assessed 59 patients in Samoa. Of those, 39 were clinically diagnosed with Parkinson’s disease. Blood testing on 49 patients found 14 carried the PINK1 genetic mutation linked to a form of early-onset Parkinson’s.

Among patients with early symptoms, roughly 75 percent to 80 percent had the mutation.

The findings suggest a higher-than-expected genetic burden in Samoa compared with global data, where such mutations account for a much smaller share of Parkinson’s cases.

Donnelly said the Pacific population may experience Parkinson’s differently, which can delay recognition. “We think this presents in a different way, so at times it’s not recognized,” he said.

Globally, Parkinson’s is most common in people over 65. But in Samoa and other Pacific populations, the disease is appearing earlier, sometimes decades sooner. One patient described in the research began showing symptoms at age 12.

The PINK1 gene plays a role in maintaining healthy mitochondria, the parts of cells that produce energy. When the gene malfunctions, damaged mitochondria can build up, eventually impairing brain cells involved in movement.

While rare worldwide, the mutation appears more common across parts of the Pacific. Donnelly pointed to migration patterns as a possible explanation, with similar variants identified in Guam, the Philippines and Malaysia.

“This tells us something about how the gene came from Taiwan through the Philippines and into the western part of Polynesia through migrations over generations,” he said.

The research also highlights structural challenges in care. Samoa does not have a resident neurologist and access to medication can be inconsistent.

“A frequent patient concern was shortages of Sinemet, which would come every one to two months and is a real problem for quality of life,” Donnelly said.

He said diagnosis still depends on clinical assessment rather than a single test, making early detection difficult in settings with limited specialist access.

“For a diagnosis of Parkinson’s disease, there’s no blood test and no brain scan,” he said. “It requires careful history-taking and physical examination.”

That gap has broader implications. Without early diagnosis, patients may miss the window for interventions that could slow disease progression, particularly as research moves toward gene-based therapies.

Donnelly said genetic forms of Parkinson’s, like those linked to PINK1, offer a pathway for earlier detection and more targeted treatment.

“We do have the possibility of finding patients before they actually manifest with Parkinson’s,” he said. “If we are to reverse a process, it’s best to reverse that process when there are only very minimal problems.”

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Future work will focus on expanding clinics in Samoa and nearby Pacific nations, including Tonga, and building local capacity for diagnosis and treatment. Researchers also plan to explore wearable and biological markers to better track the disease.

The study’s findings could extend beyond the Pacific. Donnelly said understanding how genetic Parkinson’s develops may help inform treatment for more common forms of the disease.

“What’s good for PINK1 Parkinson’s is not just finding a solution to a small proportion of patients,” he said. “It may very well be that this is good for other etiologies of Parkinson’s disease.”

For patients in Samoa, the impact is immediate. Many had never heard of Parkinson’s before being diagnosed during the study. “I told people they had Parkinson’s disease, and they said, ‘What’s that?’” Donnelly said.

He said building awareness, improving access and advancing research must happen together. “We really need to work hard on a cure,” he said.

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