Growth mixture modelling of HIV-exposed uninfected children under five in sub-Saharan Africa

In many parts of sub-Saharan Africa, a quiet public health success has created a new challenge. Decades of effort to stop mothers from passing HIV to their babies have worked remarkably well; today, the vast majority of children born to mothers with HIV are born without the virus. These children, known as HIV-exposed uninfected, are a growing population. Yet, despite being free of the virus, they often face a different kind of struggle. Even when their mothers take life-saving medication to suppress the virus, these children are more likely to be shorter and lighter than their peers who were never exposed to HIV. Scientists have long suspected that the reasons for this are complex, involving a mix of biology, poverty, and the environment, but they have struggled to see the full picture because they often looked at the group as a whole, assuming all these children grow in the same way.

A new study challenges that assumption by looking closer at the individual stories within the group. Researchers gathered data on nearly 740 children from birth until they were five years old across four countries: Malawi, South Africa, Uganda, and Zimbabwe. Instead of calculating a single average growth rate for everyone, they used a statistical approach that acts like a prism, splitting the group into smaller, distinct clusters based on how the children actually grew over time. This method revealed that these children do not all follow the same path. Instead, they fall into three very different categories for both height and weight. For height, one group remained severely stunted throughout childhood, a second group showed only mild to moderate delays, and a small third group grew well enough to catch up to standard health benchmarks. For weight, the patterns were similar, with some children remaining underweight, others staying in a stable but slightly low range, and a small group showing significant recovery over time.

The study found that where a child lived mattered significantly for weight growth trajectories, but less so for height. Children in South Africa were far more likely to belong to the groups that recovered or grew well, while children in Malawi were more likely to remain in the severe underweight categories. However, for height, no significant differences were observed between the countries, suggesting that chronic stunting is influenced by factors common across these settings rather than national context alone. The data suggests that the environment plays a massive role. Children whose families had access to private flush toilets, electricity, and whose mothers held formal jobs were significantly more likely to be in the healthy growth groups. In contrast, the severity of the mother's HIV infection or her immune system count had very little to do with which growth path her child followed. This points to a clear conclusion: the barriers to healthy growth for these children are largely structural, rooted in household conditions and national resources, rather than the virus itself.

The researchers also looked at the type of medication the mothers took, noting some interesting patterns. Children whose mothers were on certain newer drug regimens appeared less likely to fall into the moderate stunting group compared to those on older, more complex drug combinations. However, the authors are careful to note that this finding is not yet proven and requires confirmation. Because the different drug types were used in different countries at different times, it is difficult to separate the effect of the medicine from the effect of the country's overall health system and wealth. The study treats this as a clue for future research rather than a final answer. What is certain, however, is that the old view of these children as a single, uniform group is incorrect. They are a diverse population with distinct needs. The study concludes that to help these children thrive, medical care for HIV must be paired with broader improvements in living conditions, such as better sanitation and economic support, because the path to healthy growth is paved by more than just medicine.