Discussion
As demonstrated in this study, SCD is a serious disease in the
aboriginal population of the Gudalur Valley, as there is a substantially
higher risk of premature death. . Despite the high
prevalence of SCD among the aboriginal population, there have been only
a few studies documenting the causes of death and mortality
rates.16 The mortality rate identified in this study
is comparable to that observed in Brazilian patients (16.8 %) with
SCD.17
Based on our newborn screening data we found an SCT rate of 17.1% and a
SCD rate of 1.1% respectively. The SCT rate of 8.4% by Hb
electrophoresis could be falsely low because of duplications as some
individuals would have been tested more than once as their Unique ID
numbers were recorded inaccurately. Of the 16 newborns detected to have
SCD screened over 7 years (Dec 2011 – 2018), there were no deaths in
the <5 age group. This low mortality is intriguing as it
contrasts with other studies in low resource
settings18,19 and especially since none of the
patients received prophylactic penicillin or pneumococcal vaccine.
However, three of the 16 <5 children were admitted at GAH with
respiratory infections and one with acute splenic sequestration
requiring blood transfusion. Survival of all the <5 children
in this aboriginal SCD population may thus, potentially, be related to
timely medical care.
Seventy percent (70%) of deaths were in the 6-29 age group, with the
19-29 y age group having the highest mortality (45.4%) with 24.6% of
deaths in the 6-18 age group. In the study from Brazil, out of 281 SCD
deaths, most occurred in the 6-11 year age group
(35.9%)16.
The median age of death in the non-SCD aboriginals population of Gudalur
during the study period was 55 years, which is 20 years more than the
median age of death of 25 years in those with SCD. These data suggest
significant premature mortality in this SCD aboriginal population. The
high rate of early mortality reported in this study stands in contrast
to the report by Feroze et al from the adjacent district of Wayanad
which suggested that SCD disease is of a milder phenotype in the
aboriginal population.10 As the authors state, their
study of 23 patients with SCD was too small to draw any conclusions
about disease phenotype. Further, they provided no details of the
setting in which the individuals received medical care or the
completeness of the collection of clinical complications. It is of
interest that the authors report the differences in literacy and
outcomes between different tribes in the area. They too observed that
the Paniyas had the lowest literacy and the highest mortality. Thus, the
study of disease phenotype in aboriginal populations who are faced with
extreme isolation and severe disadvantage must be carried out in the
context of comprehensive care, close follow up and surveillance, and
accounting for social determinants of health.
The predominance of deaths in males is inconsistent with the overall
cohort characteristics (Table 1) but is consistent with the greater
survival in women as reported in other studies17,20
Just under half the deaths occurred at home despite the availability of
free government ambulance services and free medical care at GAH. The
persistence of barriers to care in a community owned, community centered
system of care in this extremely disadvantaged community bears further
investigation.
The causes of death in our SCD population were the sequelae of the
disease itself. None of these patients died of non-communicable
diseases, suicides, or trauma, which were the common causes of death in
the non-SCD aboriginal community. In our cohort, the overwhelming
majority of the deaths occurred due to acute chest syndrome, anemia, and
sepsis which have been described as leading causes of death in other
studies.21,22 The absence of deaths due to trauma can
be explained by the fact that, unlike the non-SCD aboriginal population,
they do not undertake hazardous work.
The Paniya tribe formed the greater part of the diagnosed SCD cases
(64%), which is consistent with their being the largest group,
constituting 58% of the aboriginal population in the Gudalur Valley. It
is not surprising that all the deaths occurred in the Paniya tribe. They
constitute the most disadvantaged of the four aboriginal groups and
were, until recently, bonded laborers, a modern form of slavery. Despite
their liberation from bonded labor, the Paniyas continue to experience
several ’vulnerability traps’ of isolation, education
deficits,10 indebtedness, alcohol use, loss of
community bonds, and traditional leadership. These factors may explain
why health outcomes in the Paniya population continue to be poorer than
the other aboriginal populations in the area. These findings may suggest
that improving health outcomes in this vulnerable population, would
require a broad strategy that addresses the social determinants of
health and their intersections with healthcare delivery and outcomes. It
is noteworthy that although the Mullu Kurumbas form only 7% of the
population, 17.8% of the SCD patients were from this group. This is
probably because of the practice of endogamy within this small tribal
community
Observed mortality has decreased between 2008 to 2018. Early screening
for SCD and the availability of a comprehensive health system with
community-based programs may account for some of this improvement. It
may also be secondary to higher economic and social status resulting
from increased accessibility and availability of education and
employment.
A major limitation of the study is that many of the deaths occurred
outside the hospital setting. However, since the study was conducted in
the context of a community directed and community based comprehensive
care, we are confident that we have been able to track all births and
deaths in this community. All aboriginal deaths in this area are
reported to the Area Nurses and AMS (Aboriginal Advancement Society)
members, who support and are also often present for the last rites.
Deaths of individuals working outside the area are uncommon but are also
reported. The Area Nurses are all from the aboriginal community and have
extensive personal connections. Of note, the accurate age of the older
adults in the aboriginal population is difficult to determine because of
the absence of birth certificates and varied self-reporting of age. The
age of death in this group was determined using the village census list.
However, the age of the younger people was accurate as it was taken from
their birth records which are more organized since 1990 when ASHWINI
started and a Unique ID number was given to each individual.
We have presented the results over 11 years and hence could not account
for multiple population-level changes that may have occurred during the
study period. As there were improvements in the educational and
financial conditions within the aboriginal population during this
period, the decrease in mortality rate observed cannot be attributed to
the availability of comprehensive and integrated sickle cell care alone.
Furthermore, the events preceding home deaths were analyzed and
documented using WHO VA tool12. The causes of
mortality recorded in this survey may not be entirely reliable
considering the time that may have elapsed since death, introducing
recall bias. Also, there could have been more than one reason for death,
but we only recorded the primary cause of death.
In conclusion, the data presented in this manuscript indicate that SCD
is a disease with high premature mortality among the aboriginal
population of the Gudalur Valley. The recognition of the severity of
SCD in this population provides the rationale for the design and
implementation of newborn screening and comprehensive care for SCD.
These programs must also address the socioeconomic and cultural barriers
to the delivery of care to these extremely disadvantaged aboriginal
populations.
Conflicts of Interest: None declared
Acknowledgments: We acknowledge Ms.Malathi Manikandan and Ms.
Pradeepa for the data collection. We thank Drs. Anna Oommen, Roshina
Sunny, and Meredith Brooks for their valuable advice. We thank the
Government of Tamil Nadu for their support.
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