According to the United Nations, there are over 370 million native or indigenous peoples residing in approximately 90 countries . In the United States (US), as of the 2010 Census, there were approximately 5.2 million American Indian or Alaska Native (AIAN) individuals, which is a growth of almost 25% over 10 years [2, 3]. This population is expected to reach 8.6 million by 2050 . At the same time, the AIAN population aged 60 and older is expected to increase from just over 600,000 in 2010 to approximately 1.8 million in 2050 .
The United States Preventive Services Task Force (USPSTF) recommendation for female adults aged 65 and older (up to 75) includes having a biennial mammogram to screen for breast cancer . The USPSTF also recommends screening for those aged 50 and older (up to 75) for colorectal cancer using fecal occult blood testing (every 5 years), sigmoidoscopy (every 5 years), or colonoscopy (every 10 years) . The existing literature for AIAN individuals is sparse relative to other groups, especially related to cancer screening among older AIAN adults.
The diagnosis of late stage cancer is a predictor of lower survival rates in those diagnosed . In 1987, an estimated 18.6% of American Indian (AI) women aged 50-59 had reported receiving a mammogram . More recent estimates (e.g. California in 2001) indicate gaps in screening in the last two years among AIAN women, as compared to White women, this gap persists among those with incomes below 200% of the federal poverty level, at 61% of AIAN individuals lower than White (71.6%); Latino (66.5%); Asian (63.2%) and African American individuals (72.8%) .
Nationally (rates calculated from the Behavioral Risk Factor Surveillance System [BRFSS] 1999-2002 and 2004), the percent of female adults aged 40 and older with mammography in the past two years was 76.2% among non-Hispanic White adults and 69.0% among AIAN adults . The rates of women aged 40 and older receiving a mammogram within the past 2 years were lowest for AIAN adults (72.8% in 2005; 62.7% in 2008); as compared to White adults (67.4% in 2005; 67.9% in 2008); Black adults (64.9% in 2005; 68.0% in 2008), and Asians adults (54.6% in 2005; 66.1% in 2008) . Here, comparisons within all other races including Hispanic or Latina ethnicities shows an increase in the rates of receiving a mammogram from 2005 to 2008, that is, all but for AIAN individuals . Additionally, the age-adjusted cancer incidence rates for all cancer sites across all races dropped from 1990 to 2004, except for AIAN individuals . The incidence rate of invasive female breast cancer among AIAN adults was highest among those aged 65 and older from 1999-2004 . A small study (n = 550) in Washington state found rates of having ever received a mammogram at 58% for AIAN adults aged 65 and older .
Nationally, the rate of colorectal cancer screening (endoscopy in the past 5 years) in adults aged 50 and older was 43.7% and 39.5% among non-Hispanic White adults and 36.5% and 36.2% among AIAN adults for males and females respectively (rates calculated with BRFSS using 1999-2002 and 2004) . Colorectal cancer being diagnosed in the early stages (local) was measured at lower rates for AIAN adults aged 50 and older as compared to non-Hispanic White adults; at 62.2 versus 46.9 (per 100,000) for the years 2001-2004 , p.2140, Table nine. In Washington State, the rate of ever receiving colorectal cancer screening (fecal occult blood) was approximately 46% among AIAN adults aged 65 and older in a small study with 550 AIAN adults . Colorectal cancer cases among those aged 65 and older accounted for approximately 65% of all cases from 1999-2004 among AIAN individuals .
As a follow-up to screening disparities, another area of concern is that of having a usual source of care where one may receive these screening services. Indian Health Service provides primary care for just 1.9 million of the 4.3 million AIAN adults residing in the US [16, 17]. This suggests a potentially severe gap in available services to over half of AIAN individuals residing in the US. The combination of residents residing in remote rural areas and the low-level of funding to Indian Health Service has contributed to this gap in services . The coverage from IHS varies across tribes and not all AIAN adults may qualify for IHS coverage . In 2006, over 90% of AIAN older adults (age 65 and older) were enrolled in Medicare .
As a group, AIAN individuals rank low on many social and environmental indicators of health and those related to access and utilization of health care services. Nationally, over 26% of the American Indian population is living below the federal poverty level , and rates of poverty for AIAN individuals are three times higher than those reported for non-Hispanic White individuals . AIAN individuals are more likely than other racial groups in the US to have lower educational attainment and face economic hardships [21, 22]. Additionally, AIAN adults aged 65 and older were more likely to report having no health insurance compared to their non-Hispanic White counterparts (4.1% compared to 1.5%) (BRFSS data 1999-2002 and 2004-2005) .
These social determinants of health (high poverty and lower education) increase the risk of having poor access to health care services , including cancer screening services. This is especially true for older adults who may have more barriers (psychological and physical) in access to health care services (e.g. transportation, disabilities, distance, perceived barriers) [24, 25]. Contextual factors including environmental characteristics (i.e. distance to resources such as food or health care services) of one’s community or the socio-economic characteristics of one’s neighborhood or working environment play a key role in one’s overall health behaviors [26, 27].
A small study of rural AIAN adults identified lack of access to medical personnel and long travel distances as barriers to accessing cancer screening . Rural areas also suffer from disproportionate gaps in health care services, where rural residents also suffer disproportionate disability and disease when compared to their urban counterparts [29–34]. Additionally, a majority of AIAN individuals live in urban areas, where Indian Health Services has a limited infrastructure in place with highly variable health care services , p5.
Thus, the combination of social determinants of health and older age and infrastructure of one’s environment compound the risk impacting AIAN older adults. The relative gap in research on this vulnerable population provides compelling evidence of the need to understand more about the AIAN older adult experience with regard to accessing and utilizing health care services. Furthermore, older AIAN individuals represent a vulnerable and understudied group in which the cancer burden is expected to grow .
This study sought to identify potential disparities in the availability and accessibility of health care services and the utilization of screening services for AIAN individuals aged 65 and older. We used county-level analyses that takes aggregate data across the US and identifies whether there are gaps in available service, access to providers and utilization of cancer screening services in areas with a higher proportion of AIAN individuals, which overlap with rural areas in many cases. We had three overall objectives in the current study. First, we measured the overall rates of unmet breast and colorectal cancer screening among AIAN older adults. Second, we identified socio-demographic characteristic of areas with a higher concentration of AIAN individuals. Third, we identified whether disparities were present with regard to geographic barriers in accessing cancer screening services. Furthermore, this study examined whether individuals likely to face these geographic barriers were also likely to have lower screening rates than those in other areas.