Research Roundup December 2020

Research Roundup: December 2020

Our monthly column highlights recent studies of Adverse Childhood Experiences (ACEs): causes, consequences, and the interventions that work.

There are many research challenges associated with examining outcomes that occur long after exposures in childhood. As a result, studies about the effects of ACEs on outcomes in older age are rare compared to those looking at impacts in young adulthood or mid-life. However, these studies are especially important because the ACE framework proposes that adverse experiences in childhood affect health across the entire life course- that is, the negative impacts of ACEs don’t disappear after a certain age. In this month’s research roundup, we review two recent articles about the potential impact of ACEs on older adults.

Adverse Childhood Experiences were associated with functional limitations and dementia in two studies of older Japanese adults

Using the Japan Gerontological Evaluation Study (JAGES) cohort, researchers found that higher ACE scores are linked to higher-level functional limitations1 and dementia2 among adults aged 65 and older. The JAGES cohort is a population-based sample of older adults living in Japan, and was created to examine social factors that contribute to healthy (and unhealthy) aging.3 One-fifth of the sample received an additional survey module asking them about their experience of ACEs. The strengths of both studies include their large sample size, nationally representative study sample, and ability to assess social and economic conditions in adulthood that may be related to both ACE exposure and health risk.

Life course models

One important question that both studies attempt to answer is the following: how do ACEs cause poor health outcomes in later life? In life course epidemiology, there are several different models to explain how an early-life experience might lead to poor health.4 One of them is called the chain-of-risk model. It postulates that a negative experience in infancy increases the risk of experiencing a negative experience in childhood, which in turn increases the risk of negative experiences in adolescence—and so on and so forth through the life span. This corresponds to the original ACE framework, which posits that ACEs result in poor health through a chain reaction from disrupted neurodevelopment, to social/cognitive/emotional impairment, to health risk behaviors and finally poor health. Another model is called the critical period model. This model hypothesizes that there are periods in human development where a negative exposure affects someone in a permanent and mostly irreversible way. For example, consumption of alcohol during pregnancy may result in permanent damage to the fetus. In the ACE framework, this would mean that adverse childhood experiences lead to poor health, regardless of whether that person experiences more positive or more negative exposures afterwards. Different models may be appropriate for different exposure-disease relationships. It is also possible that multiple models may explain different aspects of the exposure-disease relationship.

Study methods and findings. In both Amemiya et al.1 and Tani et al.’s2 studies, the authors found that higher ACE scores were associated with higher-level functional impairment and dementia. Because they were also able to assess education, adult socioeconomic statues, social relationships, and health behavior, they were also able to examine where this relationship might be explained by a chain-of-risk model, a critical period model, or both. They found evidence for both: adult socioeconomic status, social relationships, health behavior, and health status explained about two-thirds of the associations between 1) childhood ACEs and late-life dementia, and 2) ACEs and functional limitations.

Put another way, two-thirds of each relationship were explained by a chain-of-risk model; that is ACEs lead to poor outcomes in adulthood, which then lead to poor outcomes in later life. However, there remains one-third of the relationship that is not explained- providing some evidence that there are ways ACEs “get under the skin” in childhood and are carried through the life course to affect functional impairment and cognitive outcomes in later life.

Note: While both studies are impressive in sample size and scope of social measures included, the study of ACEs and dementia is a particularly important contribution. It is generally difficult to study risk factors for dementia because people with dementia are less able to participate in surveys and recall past experiences. By linking participants’ ACE reporting in 2013 with health system records of dementia in 2016, the authors were able to provide estimates of this relationship with a reliable assessment of both ACE exposure and dementia status.

Where do we go from here?

It will be important to replicate these studies in other populations. The JAGES cohort may differ from other older-adult populations in significant ways. First, the frequency and patterning of ACE exposure is different in Japan compared to the United States. In particular, parental loss may be more common in the JAGES cohort due to the effects of the Second World War. Sexual abuse and parental substance abuse may also be less prevalent in Japan compared to other countries.5 Second, the JAGES survey response rate was 71%, and there is some indication that people who did not participate may have been poorer and sicker than those who participated. This could result in study estimates of the effect of ACEs on poor health to be underestimated. Third, survivor bias may have impacted effect estimates. If those who suffered the worst health outcomes as a result of ACEs had already died, they would not be able to participate in the study. This would also result in study estimates being underestimated. These limitations are challenging to address. Studies in other populations may help to establish both the consistency of associations and help to identify how potential sources of bias might be minimized.

Works Cited

1 Amemiya, A., Fujiwara, T., Murayama, H., Tani, Y., & Kondo, K. (2018). Adverse childhood experiences and higher-level functional limitations among older Japanese people: results from the JAGES study. The Journals of Gerontology: Series A, 73(2), 261-266.
2 Tani, Y., Fujiwara, T., & Kondo, K. (2020). Association Between Adverse Childhood Experiences and Dementia in Older Japanese Adults. JAMA Network Open, 3(2), e1920740-e1920740.
3 Kondo, K. (2016). Progress in aging epidemiology in Japan: the JAGES project. Journal of Epidemiology, JE20160093.
4 Kuh, D., Ben-Shlomo, Y., Lynch, J., Hallqvist, J., & Power, C. (2003). Life course epidemiology. Journal of Epidemiology and Community Health, 57(10), 778.
5 Fujiwara, T., Kawakami, N., & World Mental Health Japan Survey Group. (2011). Association of childhood adversities with the first onset of mental disorders in Japan: results from the World Mental Health Japan, 2002–2004. Journal of Psychiatric Research, 45(4), 481-487.