Associations between community-level disaster exposure and individual-level changes in disability and risk of death for older Americans

Highlights

• Large nationally representative sample of older Americans.

• Temporally representative sample of disasters occurring in the US.

• Community-level disasters not associated with individual-level change in disability.

• Considers disaster presence, intensity, duration and type.

• Uses novel methodology for joint modelling of longitudinal and survival data.

Abstract

Disasters occur frequently in the United States (US) and their impact on acute morbidity, mortality and short-term increased health needs has been well described. However, barring mental health, little is known about the medium or longer-term health impacts of disasters. This study sought to determine if there is an association between community-level disaster exposure and individual-level changes in disability and/or the risk of death for older Americans. Using the US Federal Emergency Management Agency's database of disaster declarations, 602 disasters occurred between August 1998 and December 2010 and were characterized by their presence, intensity, duration and type. Repeated measurements of a disability score (based on activities of daily living) and dates of death were observed between January 2000 and November 2010 for 18,102 American individuals aged 50–89 years, who were participating in the national longitudinal Health and Retirement Study. Longitudinal (disability) and time-to-event (death) data were modelled simultaneously using a ‘joint modelling’ approach. There was no evidence of an association between community-level disaster exposure and individual-level changes in disability or the risk of death. Our results suggest that future research should focus on individual-level disaster exposures, moderate to severe disaster events, or higher-risk groups of individuals.

Introduction

World-wide, the United States (US) has been ranked amongst the top five countries most frequently experiencing a natural disaster (Guha-Sapir et al., 2015). In 2010, 738 US counties, which represent nearly one in four counties, experienced events devastating enough to qualify for a US Federal Emergency Management Agency (FEMA) disaster declaration. Most recently, FEMA reported a total of 79 major disaster declarations for 2015; during preceding years this figure reached as high as 242 (Federal Emergency Management Agency, 2016a).

Disasters have been defined as “a situation or event which overwhelms local capacity, necessitating a request to a national or international level for external assistance; an unforeseen and often sudden event that causes great damage, destruction and human suffering” (Guha-Sapir et al., 2015). Although the psychological impacts of disasters have been widely studied (DiGrande et al., 2011, Galea et al., 2005, North and Pfefferbaum, 2013), few epidemiological studies have examined the medium or longer-term health consequences of disasters beyond the realm of mental health. Clearly, disasters may result in direct injury. We hypothesized that disasters could also result in medium-term adverse health impacts through two distinct community-level mechanisms related to the physical (Sampson et al., 2016) and social (Hikichi et al., 2016) environments of the community.

First, exposure to a disaster might worsen disability through the disruption of the adapted environment that individuals had crafted around themselves to mitigate physical risks for disability. Within the healthcare system, disasters may disrupt ongoing medical care for therapies ranging from daily insulin availability to longitudinal chemotherapy courses. More subtly still, disasters may strip an individual of the adaptations he or she uses to keep a physical activity limitation from becoming a social disability. For example, consider an individual with potentially limited mobility, but who through the use of assistive devices and a careful understanding of her local geography has mapped out routes without obstacles allowing her to go to the store or church. Certainly disaster debris will undo the effectiveness of these adaptations; but even after clean-up, reconstructions along the paths of her life space may present new and difficult barriers.

Second, exposure to a disaster might operate as a community-level exposure because of its wider-ranging disruption on interlocking social support networks and institutions. Because such networks are often informal, activated only upon a contingent need, or because they involve several chains of connection, we hypothesized that there might be multiple points of brittleness that are exposed to a disaster. We hypothesized that these disruptions might unmask the social adaptations that are the counterpart to the physical and environmental adaptations just discussed. Consider, for example, an individual who does not currently suffer from a physical activity limitation. A disaster may not physically interfere with her body or home, however, the disaster might still lead to disability if it disrupts those networks and institutions on whom she depends to maintain her good health.

Current understanding of disasters' medium or longer-term influence on disability or even death is scant and is largely based on case studies of particular types of disasters or specific to certain communities; thus generalizability is unclear (Aldrich et al., 2010, Hendrickson and Vogt, 1996, Sastry and Gregory, 2013, Wade et al., 2004). We therefore proposed to study the impact of a range of disasters across an extended time period and impacting many US communities to determine the potential association of disaster exposure and subsequent disability or death.