In a recent study, researchers looked into an association between the relative age and number of siblings with the combined risk of nonfatal and fatal cardiovascular events. What the results found was that if you belong to a family with multiple siblings – such as being the second or third born child, could actually add to the risk of cardiovascular events. This particular study is considered to be the first when it comes to looking at birth order and family size, as well as taking into consideration risks of nonfatal cardiovascular events.
The World Health Organization (WHO) says that the leading cause of death across the globe is due to cardiovascular diseases (CVDs) that affect the blood vessels and the heart. Other factors are family history, lifestyle factors like smoothing and a bad diet or other factors when it comes to cardiovascular diseases such as stroke and coronary heart disease.
But aside from looking into one’s family history of CVD due to genetic predisposition, other evidence suggests that there are other aspects that factor, especially birth order but not the size of the family, which can actually have an influence on death due to cardiovascular conditions.
But, there have only been some studies that have researched the impact of family structure when it comes to nonfatal cardiovascular events. In order to get a comprehensive or overall understanding of CVD risk in terms of the impact of the family structure, there is a need to include nonfatal and fatal cardiovascular events.
A rather big observational study had participants that were aged 30 to 58 years when it began. It also showed how ‘the number of siblings and birth order can influence the risk of total cardiovascular events over a 25-year follow-up period.’
Led by Professor Peter Nilsson from the Lund University in Sweden, the research team conducted their study and published their findings in the BJM Open journal.
Here’s How They Linked Family Structure to Cardiovascular Risk
In order for the researchers to get more information about family structure, they turned to the Swedish Multi-Generation Register (MGR). According to the document, it ‘consists of data of more than nine million individuals, with information available on mothers in 97% and on fathers in 95% of index persons. Index persons are confined to those born from 1932 onwards and those alive on January 1, 1961.’
The study included information from 1.36 million men and 1.32 million women between the ages of 30 to 58 in the year 1990. By using data from death and hospital discharge records and registers between the years 1990 and 2015, they were able to determine the risk of nonfatal and fatal cardiovascular events, and also the total mortality of the participants.
They also found that such factors such as education level, socioeconomic status, marital status and certain medical conditions like diabetes also influenced their CVD risk. In order to better account for these variables, the team adjusted their analysis with these in mind. They also took into account the ‘impact of family structure on cardiovascular events.’
What is the Possible Impact of Family Structure?
When it came to family size, for those that had more than one sibling, they were considered ‘at a lower risk of death than those with no siblings.’
As for men, for those with one or two siblings, they also had a lower risk of cardiovascular incidents than that had no siblings. Meanwhile, men with four or more siblings were at a higher risk. Furthermore, men with three or more siblings were also at a higher risk of heart issues as compared to those that had no brothers or sisters.
When it came to the women, when comparing those with no brothers and sisters to those that had three or more siblings, those with siblings were at higher risk of cardiovascular incidents as well. Also, women with two or more siblings were also at a higher risk.
As for birth order, first-born siblings were at a lower risk of cardiovascular and coronary incidents compared to their siblings born after them. On the contrary though, the first-born is also considered higher risk of overall mortality than their second-born brother or sister.
Chief Medical Officer at Caption Health in Brisbane, CA , Dr. Randolph P. Martin, MD, FACC, FASE, FESC and Emeritus Professor of Cardiology at Emory University Healthcare in Atlanta, GA spoke to publication MNT, explaining his thoughts on the implications of the study.
While he was not involved in the actual research, he shared on the study, “which does not 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.”
The Study’s Limitations
Despite his not being involved in the making of the study, Dr. Martin also explained, “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.”
“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,” he added.
Moreover, Dr. Martin also shared, “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.”
In addition, he also said, “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 start with parents.”
Meanwhile, the study authors note that they understand that “more research is needed to understand the links between sibling number and rank with health outcomes.”
What Are the Implications for Public Health Policy?
The study authors share that while there are a number of limitations to the study, having a rather large sample size and very comprehensive data on family structure and hospital records is a hug strength.
They also admit that the study is more of an observational design, showing ‘the correlation between family structure and cardiovascular events’ but that it does not provide the causation.
Because of their lack of data, the research team did not account for other variables including parental socioeconomic status, diagnostic procedures, diet, smoking, and other types of lifestyle factors that play a key role in their CVD analysis and risk.
However, since social factors highly contribute to the ‘impact of family structure on health outcomes such as cardiovascular risk normally, it could benefit the public health policy in the future.
Furthermore, the study was also conducted in Sweden, which is known to have a fair welfare system. The study authors also note that “this is of public health interest as different countries endorse different policies to support families and number of children.”
They also went on to share, “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.”
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