3.2.4.3 - Health patterns, development and environment
Learn how to compare health, mortality and morbidity, and explain how development, climate, drainage, air and water interact to shape unequal health outcomes.
Comparing health, mortality and morbidity
Health includes physical, mental and social well-being; a death count captures only one part of it.
Mortality and morbidity
Mortality concerns deaths in a stated population and period. Morbidity concerns illness, impairment or disease, including non-fatal conditions.
Incidence counts new cases or episodes during an interval; prevalence measures existing cases in a population at a point or over a defined period. A long-lasting disease can have high prevalence even when new-case incidence falls. A disease causing rapid death can have low prevalence despite severe mortality. Always identify the denominator: malaria cases per 1,000 people at risk differs from deaths per 100,000 total population.
Crude rates reflect actual population composition. Age-standardised rates apply common age weights, improving comparison where one population is older. They do not remove every social or environmental difference. Life expectancy summarises mortality under the period's age-specific rates; healthy life expectancy additionally incorporates time in good health. Neither predicts the exact lifespan of an individual child.
WHO World Health Statistics 2026, using revised GHE 2023, prints global both-sex life expectancy/healthy life expectancy as 67/58 years in 2000, 73/63 in 2019, 71/61 in 2021 and 73/63 in 2023. These are rounded whole years. The pandemic interruption and subsequent recovery show that progress is reversible; rounded equality does not establish that every underlying measure or country fully recovered. Older decimal series cannot be spliced into this revised series.
To compare morbidity, ask whether diagnosis, testing and reporting are equally available. More recorded illness may indicate better detection rather than worse underlying health. Self-reported poor health adds experience, but cultural expectations and survey participation also affect responses.
Development and the epidemiological transition
The epidemiological transition describes a changing burden of disease as mortality, living conditions and population age structures change.
Improved nutrition, sanitation, vaccination and healthcare can reduce infectious disease and early deaths. More people survive to older ages, making chronic non-communicable conditions more prominent. Urban lifestyles, tobacco, inactivity and polluted air can add risk. The transition concerns the relative burden and causes of illness and death, not a claim that infections disappear or all non-communicable disease is new.
The WHS 2026 statistical annex gives 2024 under-five mortality of about 115.65 per 1,000 live births in Nigeria and 2.43 in Japan. In the same annex, safely managed drinking-water access in 2024 is about 29.90% and 98.73%. These contrasts are consistent with unequal services and development, but do not isolate water as the cause of the mortality gap. Income, maternal care, conflict, education and reporting also matter.
Countries can carry a double burden: persistent infections and undernutrition alongside diabetes, cardiovascular disease and cancer. Within a country, poorer households may face unsafe water and occupational exposure while wealthier groups have different lifestyle risks. A national average can conceal both groups. Development is therefore a set of social and economic processes, not a guaranteed linear sequence through identical stages.
For a supported explanation, connect a specific improvement to its pathway: safe water reduces ingestion of pathogens, reducing diarrhoeal illness; fewer childhood deaths alter mortality and survival. Then consider a limitation such as unreliable supply or unequal access. Do not infer an individual's health from the income category of their country.
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