Should We Be Worried About Declining Birth Rates?: An Interview With Dr Niels Jorgensen

Declining birth rates are becoming a rising topic around Europe. We speak to Dr Niels Jorgensen to gain his insights and perspective.

Declining birth rates have become one of the major causes of concern in the present day world. Authorities across the world are doing their best to address this critical issue. In this interview with Dr. Niels Jorgensen who is a world recognized andrologist we discuss the various matters surrounding infertility among men, including young men.


Why Is This Happening?

Dr. Jorgensen first of all let me thank you for the opportunity for this interview and begin by asking you the reason why fertility has been decreasing among men in Europe?

If we think of fertility in a broad sense as the number of children born, the low fertility rates in Europe as well as in other countries have multiple contributing reasons going from altered biological fertility chance to demographic reasons.

The changes in semen quality – as a marker of male fertility chance – also have multiple reasons. Overall, we know that a man’s future semen quality basically is already determined before he was born. 

The early period of pregnancy when the testicles are formed is crucial for their future function. If something disturbs the testicular development that leads to reduced semen quality in adulthood. 

Here, we mainly focus on what is called endocrine disruptors that we are all exposed to. But it is more critical for the unborn boys testicles than any time later in life. 

However, our lifestyle and what we are exposed to after we are born may also matter. 

You can say that men are born with a potential level for their future semen quality, and we may risk to lose some of this later on.

How does this compare with the rest of the developed world?

We do not have very good data from all parts of what is usually called the developed world. Having said that, I think we can say that a general characteristic is that a substantial number of men have reduced fertility potential, although there might be slight differences between populations. 

For some, that will only mean that it statistically will take them longer before their female partners become pregnant whereas others will need fertility treatment if they want to become fathers. 

We have basically no information from the developing world. However, I think we should be cautious when we describe the world into a developed and a developing part. Most countries have during the recent decades experienced a dramatic development, and a question is really how different they are when it comes to factors that will affect fertility chances.


Danish Studies

Why do Danish and Norwegian young men have the highest risk of testicular cancer and how serious is the situation?

We know that it relates to environmental factors that predominantly affect the development of the testicles before we are born as it is with semen quality. 

There are excellent, large scale population studies that have shown the environmental impact on the risk of testicular cancer. 

On the other hand, we know from other studies that some ethnicities have a lower risk of testicular cancer than others. 

Thus, the environmental factors may act on a background of different genetic susceptibility.

Why is it not the same in the neighbouring countries?

Even though the situation in Sweden is better than in Denmark and Norway, it is important to say that from a more general perspective we are more or less at the same level with a high frequency of men with poor semen quality and risk of testicular cancer. 

For testicular cancer, we know that the increase is quite pronounced in most European countries, and the increase seems steeper in countries where men used to have a lower risk.


Cause And Effect

How do everyday products such as sunscreen damage fertility?

We don’t know for sure because it is very difficult to establish the effect of individual products and even mixtures of products. The negative effect of individual chemicals is very limited, and it is only in combination with multiple others that we may see an effect. 

Secondly, it is inherently very difficult to perform experiments with humans, and thereby difficult to clearly prove effects. Thus, we will have to rely on the large sum of circumstantial evidence.

However, many everyday products do have mild endocrine disrupting properties, and we believe it is through this mode of action they may have their effects.

How does the body mass index affect fertility?

Obese men have statistically lower semen quality than non-obese men. This also makes sense from a theoretical point of view but it is important to say that not all obese men have impaired semen.


What is the association between cannabis use and fertility?

This is also a topic that really deserves additional studies. Regular users seem to have a lower semen quality than non-users. 

But it is relevant to say that findings are not unambiguous.

Do e-cigarettes have a similar effect?

It seems that use of e-cigarettes has a negative effect on semen quality, but it has only been investigated in very few studies so far.

Declining Birth Rates
Rising Issue?: Declining Birth Rates have been studied extensively in Denmark


One In Four

Is it a fact that just one in four men in the developed world has good quality sperm?

That we cannot say. It is so for the Danish population which to my knowledge is the only that have been studied in detail. 

But other studies indicate that the situation is not very different in other Western countries.

Why is the situation different in the developing world?

I will question if the statement included in the question is valid because of lack of solid data. If we think of China as part of the developing world, data from China tell us that the situation has also become critical there.

What is the impact of psychological stress on fertility? 

From what is called association studies of large populations we can see that stress is associated with lower semen quality. 

However, it has also been clear that it is only a modifying factor and not the basic reason. 

Additionally, in many studies it is difficult to see if the stress causes low semen quality or the knowledge of fertility problems causes the stress.

Some reports suggest that men who help out at home also have a reduced desire for sex. Is this true and what would be the reasons?

We only know this from one study, and it needs to be replicated before we can consider the statement as a fact. And if it is true, we will need to explore what could be the reasons. Right now, statements about reasons are mainly speculations.


What would be your advice to our readers who are mainly the youth in different parts of the world with regard to lifestyle and diet in reference to the threats to fatherhood?

First of all, don’t blame yourselves if you have a poor semen quality. It is only if you have had an extreme abuse or extreme life-style that it may be the primary reason. Most likely it is factors that you could not ‘defend’ yourselves against. 

Having said that, a healthy diet and moderate physical exercise may benefit your semen quality. 

You should avoid smoking and intake of large quantities of alcohol, Maybe, you should look around you, and see if there are obvious situations where you can reduce your contribution to the use of man-made chemicals. 

Dr. Niels Jorgensen is consultant and the chief andrologist University Department of Growth and Reproduction, Rigshospitalet in Copenhagen, Denmark. He has numerous published studies to his credit and is recognized as one of the authorities in the world on human reproduction.

Photos: Dr Niels Jorgensen and Shutterstock

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