Wednesday, July 26, 2023

Consequences of premature parental death seemingly greater for boys than for girls

But strongly linked to worse mental health and lower earnings in adulthood for both sexes

BMJ

The cumulative health and economic consequences of the premature loss of a parent may be greater for boys than for girls, suggest the findings of a large long term study published online in the Journal of Epidemiology & Community Health.

Experiencing the death of a parent before the age of 21, however, is strongly linked to poor mental health and lower earnings/unemployment in adulthood for both sexes, the data indicate.

Previously published research has pointed to a link between premature parental death and the child’s subsequent health and prosperity. But no studies have drawn on high quality registry data, and few have looked at the cumulative effects or the potential impact of gender, say the researchers.

They therefore used nationwide registry data from Finland to work out if experiencing the death of a parent before the age of 21 was associated with any of several measures of poor mental health and labour market outcomes between the ages of 26–30, and what influence, if any, gender might have.

They included nearly 1 million Finns (962,350) born between 1971 and 1986, who had reached at least the age of 30 by 2016.

The relevant registry data included parental death certificates; and medical and educational records, periods of sick leave, and tax returns for their children, nearly all of whom had completed their education and entered the labour market by the age of 30.

Around 1 in 6 (15%; 145,673) people had lost a parent before the age of 31. Less than 5% had experienced the death of their mother; nearly 12% had experienced the death of their father.

The likelihood of a parental death rose sharply with age, from under 1% before the child had reached the age of 6 to just under 5% when they were aged between 26 and 30. Fathers were nearly 3 times as likely as mothers to die before their children turned 21.

Some 65,797 people lost a parent before the age of 21, and this was associated with greater odds of a hospital admission for mental ill health than it was for those who experienced this after the age of 30.

Men seemed to be more vulnerable than women. They were 70% more likely to be admitted to hospital; the equivalent figure for women was 52%. Substance use disorders and intentional self-harm were the most common reasons for hospital admission. But this varied by gender.

Boys and young men who lost their mothers prematurely had nearly 2.5 times the odds of a hospital admission for intentional self-harm as those who lost their mothers in their 30s.

Similarly, girls and young women who lost their father prematurely were around twice as likely to have a substance use disorder than those who hadn’t experienced this. Early maternal death was also associated with a substantial (88%) increase in stress disorders.

The use of medication for mental health disorders among those who lost a parent prematurely was between 18% and 33% higher for both sexes than for those who hadn’t experienced this. Sick leave was also more likely among both sexes.

Losing a parent before the age of 21 was also associated with fewer years of schooling, lower annual earnings, and more periods of unemployment at ages 26–30 for both sexes.

The largest reduction in years of schooling (4%)—equivalent to more than half an academic year—was among girls who had lost their mothers prematurely.

The estimated effects on earnings and employment were generally larger for men, among whom the early death of a father was associated with an almost 16.5% reduction in annual earnings and 6% lower likelihood of regular employment. The corresponding estimates for women were 11% and 4%, respectively.

The key strengths of the study lie in the use of nationwide population data, comprehensive monitoring, and both secondary and primary care psychiatric health records, say the researchers.

But they acknowledge that this is an observational study, which can’t account for all potentially influential factors, such as personality traits that may have affected the associations found.

And the analysis didn’t capture mild mental health issues nor account for (shared) genetic and environmental factors in childhood, all of which may have been influential, they admit.

Nevertheless they conclude: “Early parental death is strongly associated with a higher risk of children’s poor mental health in adulthood for both males and females, but the estimated odds ratios are usually quantitatively larger for males.”

Similarly, losing a parent prematurely “is negatively associated with children’s labour market outcomes (ie, employment and earnings) in adulthood, and these associations are quantitatively larger for males.”

JOURNAL

Journal of Epidemiology & Community Health

DOI

10.1136/jech-2023-220692

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Early parental death and its association with children’s mental and economic well- being in adulthood: a nationwide population- based register study

ARTICLE PUBLICATION DATE

25-Jul-2023

Egg ‘signatures’ will allow drongos to identify cuckoo ‘forgeries’ almost every time, study finds

African cuckoos may have met their match with the fork-tailed drongo, which scientists predict can detect and reject cuckoo eggs from their nest on almost every occasion, despite them on average looking almost identical to drongo eggs.

Peer-Reviewed Publication

UNIVERSITY OF CAMBRIDGE

A selection of fork-tailed drongo clutches that have been parasitised by African cuckoos. In each photo, the right-most egg is the cuckoo egg — IMAGE: A SELECTION OF FORK-TAILED DRONGO CLUTCHES THAT HAVE BEEN PARASITISED BY AFRICAN CUCKOOS. IN EACH PHOTO, THE RIGHT-MOST EGG IS THE CUCKOO EGG view more
CREDIT: CLAIRE SPOTTISWOODE

Images and paper available at: https://drive.google.com/drive/folders/1mPYnFKIEArlXUAaFk5H7YTepezntqerj?usp=sharing

Fork-tailed drongos, belligerent birds from sub-Saharan Africa, lay eggs with a staggering diversity of colours and patterns. All these colours and patterns are forged by the African cuckoo.

African cuckoos lay their eggs in drongos’ nests to avoid rearing their chick themselves (an example of so-called brood parasitism). By forging drongo egg colours and patterns, cuckoos trick drongos into thinking the cuckoo egg is one of their own.

But drongos use knowledge of their own personal egg ‘signatures’ – their eggs’ colour and pattern –to identify cuckoo egg ‘forgeries’ and reject them from their nests, say scientists. These ‘signatures’ are like the signatures we use in our daily lives: unique to each individual and highly repeatable by the same individual.

Through natural selection, the African cuckoo’s eggs have evolved to look almost-identical to drongo eggs – a rare example of high-fidelity mimicry in nature.

A team led by researchers at the University of Cambridge and the University of Cape Town, working in collaboration with a community in Zambia, set out to explore the effectiveness of ‘signatures’ as a defence against highly accurate mimicry.

They found that despite near-perfect mimicry of fork-tailed drongo eggs, African cuckoo eggs still have a high probability of being rejected.

The findings are published today in the journal, Proceedings of the Royal Society B.

Researchers carried out field work in the Choma district of Zambia during September to November across four years. The first step was to measure the differences in colour and pattern of the fork-tailed drongo eggs and cuckoo eggs. The team found that the colour and pattern of cuckoo eggs was, on average, almost identical to that of drongo eggs, and that all the broad types of drongo egg ‘signatures’ were forged by the cuckoos.

“It is incredible how perfect the mimicry is. We have occasionally missed cuckoo eggs in the field because they looked exactly like the drongo clutch that they were found in,” said lead researcher and Zoology PhD student Jess Lund.

The second step involved ‘egg rejection’ experiments in which the researchers simulated cuckoo visits by ‘parasitising’ drongo nests with foreign eggs from other drongo nests (as a proxy for African cuckoo eggs). They then checked the nest daily to see whether the drongo parents accepted the foreign egg as one of their own, or realised it was an imposter and rejected it by removing it from their nest. The team could then test what differences in colour and pattern between the foreign egg and the drongo’s own eggs best predicted whether or not the drongo parents were tricked.

By combining results from both steps of the study, the researchers were able to create a model that predicted how often, on average, an African cuckoo would have its eggs rejected by a fork-tailed drongo host. They found the predicted rate of rejection to be 93.7%.

“We were surprised to see that so many of the cuckoo eggs were predicted to be rejected”, said Lund “Our additional simulations show this is likely due to drongos having evolved ‘signatures’ on their eggs. Even though cuckoos have evolved excellent ‘forgeries’, individual cuckoos don’t target individual drongo nests that match their own eggs. This means that for each cuckoo egg laid, the likelihood that it will be a good enough match to that drongo’s ‘signature’ is very low.”

Fork-tailed drongos have likely honed these ‘signatures’ and detection abilities through natural selection, explains Lund. “It’s very costly for drongo parents if they don’t have these skills. If they can’t tell a ‘forgery’ from their ‘signature’ their own chicks will be killed by the cuckoo when it hatches, and they will be stuck raising a ravenous cuckoo for a whole breeding season.”

The results of the study suggest that a female cuckoo may only fledge two chicks in her lifetime – only just replacing herself and her mate. Researchers say that this would not amount to a sustainable population, which presents a puzzle because African cuckoos remain a common bird in many parts of Africa.

The researchers think that the fork-tailed drongos where the research took place could be particularly good at spotting ‘forgeries’. “Perhaps this part of Zambia is a hotspot for parasitism, where drongos have particularly fine-tuned defences, and against which cuckoos stand little chance,” said Lund.

The research was supported by the DST-NRF Centre of Excellence at the FitzPatrick Institute at the University of Cape Town, the BBSRC, the Royal Society, and the Department of Zoology at the University of Cambridge, and carried out with the crucial support of a community in Zambia who find and access drongo nests.

ENDS.

Reference:

Lund et al. When perfection isn’t enough: host egg signatures are an effective defence against high-fidelity African cuckoo mimicry, Proceedings of the Royal Society B, DOI: 10.1098/rspb.2023.1125

CAPTION

Two drongo clutches parasitised by different African cuckoo females. In each clutch of eggs the cuckoo egg is on the right.

A fork-tailed drongo nest that has been parasitised by an African cuckoo (cuckoo egg on the bottom right).

A selection of fork-tailed drongo eggs, each laid by a different female, arranged in a circle.
CREDIT
Jess Lund

African Cuckoo chick.
CREDIT
Claire Spottiswoode

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