Disability Transitions and Health Expectancies among Adults 45 Years and Older in Malawi: A Cohort-Based Model

: Collin Payne and colleagues investigated development of disabilities and years expected to live with disabilities in participants 45 years and older participating in the Malawi Longitudinal Survey of Families and Health. Background: Falling fertility and increasing life expectancy contribute to a growing elderly population in sub-Saharan Africa (SSA); by 2060, persons aged 45 y and older are projected to be 25% of SSA's population, up from 10% in 2010. Aging in SSA is associated with unique challenges because of poverty and inadequate social supports. However, despite its importance for understanding the consequences of population aging, the evidence about the prevalence of disabilities and functional limitations due to poor physical health among older adults in SSA continues to be very limited. Methods and Findings: Participants came from 2006, 2008, and 2010 waves of the Malawi Longitudinal Survey of Families and Health, a study of the rural population in Malawi. We investigate how poor physical health results in functional limitations that limit the day-to-day activities of individuals in domains relevant to this subsistence-agriculture context. These disabilities were parameterized based on questions from the SF-12 questionnaire about limitations in daily living activities. We estimated age-specific patterns of functional limitations and the transitions over time between different disability states using a discrete-time hazard model. The estimated transition rates were then used to calculate the first (to our knowledge) microdata-based health expectancies calculated for SSA. The risks of experiencing functional limitations due to poor physical health are high in this population, and the onset of disabilities happens early in life. Our analyses show that 45-y-old women can expect to spend 58% (95% CI, 55%–64%) of their remaining 28 y of life (95% CI, 25.7–33.5) with functional limitations; 45-y-old men can expect to live 41% (95% CI, 35%–46%) of their remaining 25.4 y (95% CI, 23.3–28.8) with such limitations. Disabilities related to functional limitations are shown to have a substantial negative effect on individuals' labor activities, and are negatively related to subjective well-being. Conclusions: Individuals in this population experience a lengthy struggle with disabling conditions in adulthood, with high probabilities of remitting and relapsing between states of functional limitation. Given the strong association of disabilities with work efforts and subjective well-being, this research suggests that current national health policies and international donor-funded health programs in SSA inadequately target the physical health of mature and older adults. Background: The population of the world is getting older. In almost every country, the over-60 age group is growing faster than any other age group. In 2000, globally, there were about 605 million people aged 60 years or more; by 2050, 2 billion people will be in this age group. Much of this increase in the elderly population will be in low-income countries. In sub-Saharan Africa, for example, 10% of the population is currently aged 45 years or more, but by 2060, a quarter of the population will be so-called mature adults. In all countries, population aging is the result of women having fewer children (falling fertility) and people living longer (increasing life expectancy). Thus, population aging is a demographic transition, a change in birth and death rates. In low- and middle-income countries, population aging is occurring in parallel with an “epidemiological transition,” a shift from communicable (infectious) diseases to non-communicable diseases (for example, heart disease) as the primary causes of illness and death. Why Was This Study Done?: Both the demographic and the epidemiological transition have public health implications for low-income countries. Good health is important for the independence and economic productivity of older people. Productive older people can help younger populations financially and physically, and help compensate for the limitations experienced by younger populations infected with HIV. Also, low-income countries lack social safety nets, so disabled older adults can be a burden on younger populations. Thus, the health of older individuals is important to the well-being of people of all ages. As populations age, low-income countries will need to invest in health care for mature and elderly adults and in disease prevention programs to prevent or delay the onset of non-communicable diseases, which can limit normal daily activities by causing disabilities. Before providing these services, national policy makers need to know the proportion of their population with disabilities, the functional limitations caused by poor physical health, and the health expectancies (the number of years a person can expect to be in good health) of older people in their country. In this cohort modeling study, the researchers estimate health expectancies and transition rates between different levels of disability among mature adults in Malawi, one of the world's poorest countries, using data collected by the Malawi Longitudinal Survey of Families and Health (MLSFH) on economic, social, and health conditions in a rural population. Because Malawi has shorter life expectancies and earlier onset of disability than wealthier countries, the authors considered individuals aged 45 and older as mature adults at risk for disability. What Did the Researchers Do and Find?: The researchers categorized the participants in the 2006, 2008, and 2010 waves of the MLSFH into three levels of functional limitation (healthy, moderately limited, and severely limited) based on answers to questions in the SF-12 health survey questionnaire that ask about disabilities that limit daily activities that rural Malawians perform. The researchers estimated age–gender patterns of functional limitations and transition rates between different disability states using a discrete-time hazard model, and health expectancies by running a microsimulation to model the aging of synthetic cohorts with various starting ages but the same gender and functional limitation distributions as the study population. These analyses show that the chance of becoming physically disabled rises sharply with age, with 45-year-old women in rural Malawi expected to spend 58% of their estimated remaining 28 years with functional limitations, and 45-year-old men expected to live 41% of their remaining 25.4 years with functional limitations. Also, on average, a 45-year-old woman will spend 2.7 years with moderate functional limitation and 0.6 years with severe functional limitation before she reaches 55; for men the corresponding values are 1.6 and 0.4 years. Around 50% of moderately and 60%–80% of severely limited individuals stated that pain interfered quite a bit or extremely with their normal work during the past four weeks, suggesting that pain treatment may help reduce disability. What Do These Findings Mean?: These findings suggest that mature adults in rural Malawi will have some degree of disability during much of their remaining lifetime. The risks of experiencing functional limitations are higher and the onset of persistent disabilities happens earlier in Malawi than in more developed contexts—the proportions of remaining life spent with severe limitations at age 45 in Malawi are comparable to those of 80-year-olds in the US. The accuracy of these findings is likely to be affected by assumptions made during modeling and by the quality of the data fed into the models. Nevertheless, these findings suggest that functional limitations, which have a negative effect on the labor activity of individuals, will become more prominent in Malawi (and probably other sub-Saharan countries) as the age composition of populations shifts over the coming years. Older populations in sub-Saharan Africa are not targeted well by health policies and programs at present. Consequently, these findings suggest that policy makers will need to ensure that additional financial resources are provided to improve health-care provision for aging individuals and to lessen the high rates of functional limitation and associated disabilities. Additional Information: Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001435.