Does Low Birth Weight Increase the Risk of Dementia?

Women who give birth to babies weighing less than 2.2 kg are more likely to have memory and thinking problems later in life than those who give birth to babies without a low birth weight. This is according to a study published in the online edition of Neurology®, the medical journal of the American Academy of Neurology. The effects on memory and thinking skills were equivalent to aging by one to two years in those born with a low birth weight.

The study does not prove that giving birth to a low birth weight infant leads to memory and thinking problems. It merely shows a correlation. Previous studies have shown that people born with a low birth weight have a higher risk of cardiovascular disease and high blood pressure. The study found that a history of having a low birth weight child may also be a marker for poorer cognition later in life.

How Birth Weight and Cognitive Problems are Linked

The study involved 15,323 women, whose average age at the end of the thinking and memory tests was 62 years. All participants had given birth at least once. Of all the participants, 1,224, or 8%, had given birth at a low birth weight. Low birth weight was defined as less than 5.5 pounds in pregnancies (2.2 kg) of more than 20 weeks’ duration. Participants completed a questionnaire about their pregnancy complications, birth history, birth weight and other information. They also completed a series of thinking and memory tests.

The researchers then combined the average scores of the two tests on memory and the participants’ ability to react quickly and accurately to a situation, as well as the two tests on learning and working memory. A higher score indicates better memory and thinking. On average, the difference between the results of the participants with and without low birth weight was -0.06 for the speed and attention tests and -0.05 for learning and working memory. This is comparable to the difference associated with one to two additional years of life in this population.

The results were similar after the researchers accounted for factors that could influence both birth weight and cognitive function, such as age, smoking status and hypertension. The results were also similar when the researchers did not consider individuals with preterm births, pregnancies with twins or other multiples, or those with pregnancy-related hypertension. In addition, they found that the more low birth weight births those affected had, the lower the values were.

Future research is needed to confirm the findings and investigate whether screening women with a history of low birth weight deliveries for cognitive problems and interventions to promote their brain health could help prevent or delay later cognitive impairment and dementia. One limitation of the study is that most of the women were non-Hispanic whites, so the results may not be generalizable to other populations. The study was supported by the National Institute of Mental Health, the National Institute of Environmental Health Sciences, the National Institute on Aging and the Office of Research on Women’s Health.