Temporal trends in infant death (Kenya)
It is important to know the sequence of temporal trends of death at different ages as it is often wavy, showing positive and negative inversions depending on advances and setbacks in environmental conditions.
Temporal change in infant deaths in under 5s in Kenya is a good example of these trends: the rate went from 102.3 per 1,000 in 1990, to less than half that in 2015 (49.4). But a more detailed analysis reveals that in 1990 the positive trend to reduction had already inverted and a continuous rise in mortality was under way, which in 1996 inverts again, to gradually drop until 2003 (when it again reached1987 levels), accelerating rapidly from then on.
Temporal trends in health indicators, be it size by age or mortality index, are waves because they fluctuate according to the temporal trends of their environmental determinants.