Number of siblings and cardiovascular health: Study explores link – Medical News Today

Written by Deep Shukla on May 30, 2021 Fact checked by Jessica Beake, Ph.D.

According to the World Health Organization, cardiovascular diseases (CVD), which affect the heart and blood vessels, are the leading cause of death globally.

Family history and lifestyle factors such as smoking and an unhealthy diet are well-established risk factors for cardiovascular diseases, including coronary heart disease and stroke.

Besides a family history of CVD largely influenced by genetic predisposition, there is also evidence to show that family structure, especially birth order but not family size, can influence the risk of death due to cardiovascular conditions.

However, only a few studies have looked at the impact of family structure on nonfatal cardiovascular events.

A comprehensive understanding of the impact of family structure on CVD risk requires the inclusion of both fatal and nonfatal cardiovascular events.

A large observational study involving people aged 3058 years at onset now shows that the number of siblings and birth order can influence the risk of total cardiovascular events over a 25-year follow-up period.

A team of researchers led by Prof. Peter Nilsson at Lund University in Sweden conducted this study. Their findings appear in the journal BMJ Open.

To obtain information about family structure, the researchers used the Swedish Multi-Generation Register (MGR). The register includes records of biological parents of more than 95% of the population born after 1931 and alive in 1961, thus providing an exceptionally large dataset.

The study included data from 1.36 million men and 1.32 million women aged 3058 years in 1990. They determined the risk of nonfatal and fatal cardiovascular events as well as total mortality among these individuals using data from death and hospital discharge registers between 1990 and 2015.

Factors such as socioeconomic status, education level, marital status, and medical conditions such as diabetes can influence CVD risk.

The team adjusted their analysis to account for the influence of these variables and isolate the impact of family structure on cardiovascular events.

In terms of family size, men and women with more than one sibling were at a lower risk of death than those with no siblings.

Men with one or two siblings had a lower risk of cardiovascular events than those with no siblings, while those with four or more siblings had a higher risk.

Men with three or more siblings also had a higher risk of coronary events compared with no siblings.

Similarly, compared with women with no siblings, women with three or more siblings had a higher risk of cardiovascular events. In addition, women with two or more siblings had a higher risk of coronary events.

In the case of birth order, first-born individuals had a lower risk of cardiovascular and coronary events than those who were born later.

In contrast, first-born individuals had a higher risk of overall mortality than second-born siblings.

Medical News Today spoke with Dr. Randolph P. Martin, MD, FACC, FASE, FESC, Emeritus Professor of Cardiology at Emory University Healthcare in Atlanta, GA, and Chief Medical Officer at Caption Health in Brisbane, CA, about the implications of this study.

Dr. Martin was not involved in the research, but noted that the study, which does involve over 2.6 million Swedish citizens born between 1932 and 1960, is a large study, but it is an observational study. It only shows an association not a cause and effect relationship.

There are significant limitations [to the research] in the fact that there was no data gathered from these people about such things as their BMI, their smoking history, their diet, and their exercise habits, continued Dr. Martin.

So, we do have somewhat limited data about these individuals in areas where we know there are cardiovascular risks, including being overweight, a smoker, having a poor diet, not exercising regularly, and additional socioeconomic stressors.

Additionally, Dr. Martin noted, We do not have a lot of information about siblings in the family who may have died, and what rank they were. That could have told us more about risk factors in the family.

Another limitation in the data we do have is that these individuals were all born between 1932 and 1960. Awareness of cardiovascular risk factors and prevention grew dramatically during that period of time. Those born in the late 50s may have had less of a risk factor than those born in the 30s, for example awareness of the impact smoking could have on health, for example, was not as well known in the 30s and 40s.

The big takeaways from this study are these: First, we need more data; second, the study further solidifies the need for good cardiovascular health habits, which starts with parents.

The authors of the paper also recognize that more research is needed to understand the links between sibling number and rank with health outcomes.

While the studys strengths included a large sample size and comprehensive data on family structure and hospital records, it also had some limitations.

The researchers note that the study, owing to its observational design, only shows a correlation between family structure and cardiovascular events and does not establish causation.

Due to the lack of data, the researchers were also unable to account for variables such as diagnostic procedures, parental socioeconomic status, smoking, diet, and other lifestyle factors that could have influenced their analysis of CVD risk.

Since social factors are likely to contribute to the impact of family structure on health outcomes, including cardiovascular risk, the studys results could influence public health policy.

Significantly, this study was conducted in Sweden, which has a generous welfare system. The authors observe that this is of public health interest as different countries endorse different policies to support families and number of children.

Future research should be directed to find biological or social mechanisms linking the status of being first born to lower risk of CVD, as indicated by our observational findings, state the authors.

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Number of siblings and cardiovascular health: Study explores link - Medical News Today