Incidence and prevalence of Parkinson's disease among Navajo people living in the Navajo nation

Abstract

Parkinson's disease (PD) is largely unstudied among American Indians. Unique populations might harbor clues to elusive causes. We describe the incidence and prevalence of PD among Navajo people residing in the Navajo Nation, home to the largest American Indian tribe in the United States. We analyzed 2001-2011 inpatient and outpatient visit data for Navajo people obtained from the Indian Health Service, which provides health care to American Indian people living on the Navajo Reservation. Cases were defined by at least two inpatient or outpatient visits with the diagnosis of PD. Crude and age-adjusted incidence and prevalence rates were calculated overall as well as by age, sex, region of residence, and time period. Five hundred twenty-four Navajo people with median age-at-onset of 74.0 years were diagnosed with PD during the study period, yielding an average annual crude incidence rate of 22.5/100,000. Age-specific incidence was 232.0 for patients 65 years of age or older and 302.0 for 80 years of age or older. Age-adjusted incidence was 35.9 overall (238.1 for ≥65 years), was higher in men than in women (47.5 vs. 27.7; P<0.001), varied by region (P=0.03), and was similar between time periods (2002-2004 vs. 2009-2011). The age-adjusted point prevalence rate was 261.0. The rate of PD among Navajo People appears to be as high as or higher than rates reported in many other populations. Rates increased to the highest age group, consistent with population-based studies. Further investigation is warranted to examine risk factors for PD in this remote population.

Variations in Incidence and Prevalence of Parkinson’s Disease in Taiwan: A Population-Based Nationwide Study

“…Our study showed a moderate but significant increase in PD incidence in Taiwan, which is inconsistent with the reports from previous studies that presented a stable [ 4 , 5 , 7 , 9 , 10 ] or decreasing trend [ 8 , 22 ]. Studies conducted in Japan (1992 and 2004) [ 5 ], Argentina (2003 and 2008) [ 9 ], Indian Navajo Nation of the US (2002–2004 and 2009–2011) [ 10 ], and France (2005 and 2010) [ 7 ] all demonstrated relatively stable PD incidences. A decreasing trend in incidence of PD was observed in a UK study reporting an average reduction by 6% annually from 1999 to 2009 [ 22 ].…”

“…Many studies reported that the prevalence of PD had increased over the past decades, partially attributed to the increasing older population worldwide [ 3 – 8 ]. By contrast, most studies showed no substantial changes in the incidence of PD over time [ 4 , 5 , 7 , 9 , 10 ]. Moreover, race/ethnic variations in PD incidence and prevalence have been reported [ 11 ].…”

Statin therapy prevents the onset of Parkinson disease in patients with diabetes

“…In this population‐based study of diabetic patients, we observed a higher risk of PD in female relative to male subjects. In general population studies, PD incidence is a little higher in males, but in diabetic populations, females have higher risk of PD; the mechanisms are not still known. The possible mechanisms may be related to estrogen effects on dopaminergic neurons and pathways in the brain .…”

Huntington disease among the Navajo: A population-based study in the Navajo Nation

“…To our knowledge, this is the first epidemiologic study of HD in an American Indian tribe and the only report detailing the absence of HD in any population. Taken with studies of amyotrophic lateral sclerosis 3 and Parkinson disease, 4 these data point to differentially distributed neurodegenerative disorders among American Indians and other populations. Research into the reasons underlying these contrasts could yield better understanding of often cryptogenic and universally incurable brain disorders.…”

“…Methods. The e-Methods on the Neurology ® Web site at Neurology.org and previous articles by this group 3,4 describe the methodology in detail. We sought to determine average annual incidence and point prevalence rates of HD among Navajo residents of the Navajo Nation during 2001-2011.…”