Prevalence of cerebrovascular calcifications in indigenous Bolivian Tsimane and Moseten

Background: Intracranial arteriosclerosis has been increasingly recognized as an etiological factor contributing to cognitive impairment. Indigenous Tsimane and Moseten, Amerindians of the Bolivian Amazon with physically-active subsistence lifestyle, are reported to have lower prevalence of dementia (Gatz et al., Alzheimer’s Dement, In press) and coronary artery disease (Kaplan et al.,Lancet,2017) than Western populations. We assessed the prevalence of intracranial arteriosclerosis, cerebrovascular calcifications, and leukoaraiosis in these populations and investigated their relationship with brain atrophy and cognition.
Method: 155 participants aged ≥60 (60.6% females) underwent a non-contrast computed tomography scan and cognitive testing. Visual rating scales were used to evaluate global cortical atrophy (GCA, simplified Pasquier), medial temporal atrophy (MTA, Scheltens), internal carotid artery (ICA) calcifications extent and morphology (Babiarz/Kockelkoren), lenticulostriate arteries (LSA) calcifications (de Brouwer), deep and periventricular leukoaraiosis (Fazekas). The maximum density (Hounsfield units) of LSA calcifications and the presence of infarcts and vertebral arteries (VA) calcifications were also evaluated.
Result: Virtually all participants presented vascular calcifications in ICA (99.3%), LSA (87.4%), and VA (98.5%) (Fig.1,2). ICA calcification morphology was continuous in 58.7% and irregular/patchy in 40.5%, indicating medial and intimal pathology, respectively (Fig.3). In 13.2% of cases, the LSA calcifications were surrounded by parenchymal calcifications in the basal ganglia (Fig.4). Most cases showed no radiological sign of infarcts or leukoaraiosis. ICA calcifications correlated with age (P<.0001) while other calcification locations showed little association with age. LSA calcifications were greater in men than women (P<.01) with sex differences minimal for other calcification locations. After controlling for age and sex, ICA, LSA, basal ganglia and VA calcifications were related to greater GCA (all P<.05). LSA calcification density was significantly related to greater GCA and MTA, and to poorer visuo-constructional ability (all P<.01). Prevalence of ICA and VA calcifications were higher compared to those reported in a population-based European sample (79% and 16.9%, respectively; Vinke et al.,Neurobiol.Aging,2021). (Fig.5)
Conclusion: Despite the low prevalence of dementia and coronary artery disease, cerebrovascular calcifications are commonly observed in this indigenous Bolivian population, and are associated with greater brain atrophy. Their underlying pathogenetic mechanisms remain unclear, but the high prevalence of infectious and inflammatory disorders might play a role.