The South Asian Middle-Aged Risk Tracking for Brain Health (SAMARTH) study: Participants’ characteristics and effects of metabolic impairment

BACKGROUND

South Asians (SAs; India, Afghanistan, Bangladesh, Bhutan, the Maldives, Nepal, Pakistan, and Sri Lanka) comprise nearly 25% of the global population and represent the fastest-growing ethnic group in the United States. They also experience a high prevalence and a particularly aggressive profile of metabolic impairment (MIm). Despite this, SAs remain markedly understudied in ADRD. The South Asian Middle-Aged Risk Tracking for Brain Health (SAMARTH) study is the first longitudinal, US-based study of cognition in SAs, designed to examine the role of MIm in cognitive and brain aging.

 

METHODS

We recruited the first 100 SAMARTH participants, aged 45–70 years, residing in New Jersey and surrounding areas. Participants completed the UDS cognitive test battery along with metabolic, anthropometric, psychiatric, lifestyle assessments, and brain MRI, to evaluate cognitive trajectories and vascular brain markers. Recruitment sources included partnerships with community leaders, NGOs, and recruitment companies; radio and television programs, community events, and health camps; social media advertising; and electronic medical records. Participants were categorized as having or not having MIm, defined as type 2 diabetes (T2D), prediabetes (HbA1c 5.7–6.4%), or obesity (BMI >30 kg/m²). Clinical, sociodemographic, lifestyle, and psychological characteristics were compared between groups.

RESULTS

Participants were aged 56.3±6.7 years; 57% were women; 66.7% had MIm. Groups were broadly similar in sociodemographics but those with MIm had a higher age at immigration (24.8 vs. 20.7 years). The groups did not differ in lifestyle (sleep, diet, smoking, and exercise), clinical (cholesterol, systolic and diastolic blood pressure), or psychological measures (depression, loneliness). By definition, the MIm group had higher fasting glucose (96.4 vs. 84.6 mg/dL), more prediabetes (50.9% vs. 0%), and more T2D (33.8% vs. 0%) (all p<0.01). MRI of the first 20 participants who were scanned revealed lower white matter hyperintensities (p=0.05) and reduced cerebral blood flow in the precuneus (p=0.057) in MIm participants.

CONCLUSION

Our cohort addresses a critical gap in ADRD research among South Asians. These preliminary findings suggest that, even in midlife, MIm, in the absence of differences in other lifestyle or clinical factors, adversely affects cerebral vasculature. These findings suggest the importance of addressing MIm in this high dementia risk, understudied population.