Relative Roles of Medical Interventions and Infrastructure in an Urban Community’s Infant Mortality Rate: 100 Years of Infant Mortality in the City of Worcester

Abstract

Background: The infant mortality rate (IMR), defined as the number of deaths in children under 1 year of age per 1000 live births, is regarded as a sensitive measure of population health (Blaxter). This reflects the overlap between those societal factors that impact infant mortality and those that affect the health of the larger community, such as SES, nutrition, living conditions, education, employment and access to health care. In 2003, Reidpath et al showed a strong linear relation between IMR and the disability adjusted life expectancy (DALE), a more comprehensive measure of population health. They concluded that either the IMR or the DALE could stand as a proxy for the measurement of population health. Objectives: We proposed to study historic trends in the IMR of the city of Worcester, MA, the second largest city in New England with a population of 181,045 (census 2010), over a 100 year period. We evaluated trends in the overall infant mortality rate as well as by specific causes of death. We further looked at known changes in medical innovation as well as community living conditions that may have had an effect on these rates. Methods: From August through September 2012, infant death certificates housed in the Worcester City Hall, Office of the City Clerk, were reviewed and entered into an Excel spreadsheet. The first year, 1906, was selected due to a particularly high IMR. Following 1906, years were chosen at 10-year intervals through 1976. Beginning in 1986, data was available through a downloadable file. Data collected included the record number, the date of death, the age of the infant in months and years, cause of death, city of residence, and place of birth of mother. Specific causes of death were transformed into 13 general categories. A subsequent comparative analysis was performed. Results: A total of 2929 hard copy death certificates were reviewed and an additional 116 records were added through downloadable files. Because 1956 was the last year to include stillbirth in infant mortality records, analysis was conducted excluding numbers of stillbirths. In 1906, the overall IMR was 143 (per 1000 live births). By 1936, the total IMR had already dropped significantly to 52, a drop of 64%. By 2006, the IMR had dropped to 4.6, a decrease of almost 97%. Much of this drop reflected changes in the IMR due to infection, which dropped from 75 in 1906 to 15 in 1936 and to .4 by 2006. In total, the decrease in IMR due to infection was responsible for more than half of the total decrease in IMR, with 80% of the drop in infection-related IMR occurring before 1936. Over this time period, the IMR due to congenital malformations also slowly decreased from 8 in 1906, to 7.3 in 1976 and then to 2.0 in 1986 and .8 in 2006. Interestingly, 83% of the decreases in IMR due to malformation occurred after 1976. IMR due to prematurity was 34 in 1906, decreased to 14.7 in 1976 and further decreased to 6.4 in 1986 and to 3.1 in 2006. Again, 89% of the decreases in IMR due to prematurity occurred after 1976. Conclusions: The IMR in Worcester has undergone a dramatic reduction over the past 100 years, driven in large part by great reductions in number of deaths from infectious causes. Interestingly, a large part of the reduction in IMR secondary to infection occurred by 1936, prior to the development and widespread availability of antibiotics and vaccines against infectious diseases starting in the 1940s. Changes in public health infrastructure, changes in hygiene, including water, sewage and housing, and access to better nutrition and education likely played a significant role in decreased infant mortality due to infection prior to the development of medical interventions. A number of medical developments are likely responsible for decreased rates of infant mortality due to malformations and prematurity seen after 1976. These include the advent of neonatal surgery in the 1950s, the introduction of Neonatal Intensive Care Units (NICUs) in the 1960s, the use of fetal heart monitors and fetal distress as an indication for delivery by cesarean section in the 1960s to 1970s, the development of amniocentesis (for lung maturity and genetic testing) and ultrasound (for dating) in the 1970s, Roe vs. Wade in 1973, the advent of alpha fetoprotein testing and folic acid supplementation in the 1980s, and corticosteroids for fetal lung maturity in the 1980s-1990s. The large decrease in IMR due to infectious causes over the last 100 years highlights IMR’s sensitive relationship to societal factors and suggests that deteriorations in living conditions during recent difficult economic times could result in high and increasing IMRs among vulnerable subpopulations. We propose that interventions addressing societal factors could have the greatest impact in preventing infant mortality in Worcester.