This study provides evidence of rising levels of reported ill-health, as measured by the prevalence of chronic diseases and conditions and, to some extent, in poorer self-rated health, in the newer cohorts of the young-old. These did not appear to be reflected in greater functional limitation or disability although there were small increases in mobility limitation and IADL/ADL disability in the new cohort.
The major contributors to the increase in the number of chronic conditions reported were arthritis and chronic obstructive airways disease, the latter despite lower levels of smoking in the newer cohort. There are few cohort studies of changes in the prevalence of disease and where these exist, findings are equivocal. Newer male cohorts in Sweden were less likely to report no diseases but more likely to report no symptoms , whilst recent US cohorts report lower levels of cardiovascular disease but increases in asthma and musculoskeletal problems and Swedish cohorts increased stroke, myocardial infarction and diabetes. Within the US there have been equivocal reporting of trends in the prevalence of arthritis with an increased prevalence in the young-old  but decreases for even younger cohorts . Increasing prevalence of arthritis has also been found in Japan , associated with an increase in mild disability.
In support that the observed increase in the prevalence of chronic conditions is real, other countries have shown increased prevalence to be also reflected in higher rates of mortality especially from lung cancer, COPD and IHD in Danish, Dutch and Norwegian men. However there may be other reasons for trends, including earlier diagnosis and an increase of reporting of conditions. Newer cohorts may benefit from earlier detection and diagnosis which may be translated into less severe levels of disease and a longer survival from date of diagnosis. We found little evidence of increased survival, perhaps due to low statistical power, but since our data did not include date of diagnosis or severity of disease we could not fully test this hypothesis.
A limitation of our study is that the majority of information on chronic conditions was self-report and therefore our findings, as many of the other studies, may be due to increased awareness and reporting of symptoms in newer cohorts. Although arthritis has already been shown to be an important predictor of moderate to severe disability onset in MRC-CFAS, including the base cohort here , the increase in arthritis prevalence in particular may reflect a threshold shift, with those interviewed in 1996/7 reporting arthritis at a lower threshold of pain or impairment, possibly due to increased availability of new treatments. In addition our study had around 4% of each cohort with moderate or severe dementia, where self-report may be problematic. In these cases information was obtained from an informant, with potentially other biases. However previous work has shown that levels of agreement in reports of past and current health problems by informants when compared with participants free of dementia, is good, especially where the informant is co-resident as is likely to be the case for participants with moderate or severe dementia.
Our findings of increased ill-health appeared to be accompanied by a small non-significant increase in mobility limitations and ADL disability in later cohorts, since our sample had low statistical power to detect even moderate differences and the five-year interval between cross-sections is fairly short. Cohort differences in impairments, functional limitations and disability have been confined mostly to the US and Scandinavia. Studies from the US have pointed to a decline in both ADL and IADL in recent decades, while findings from other studies are less clear. One group of studies report later cohorts to have less hearing impairment  and improved physical functioning, the latter generally in mobility and IADL disability rather than in more severe ADL disability, which appears to remain constant [41–43]. The remaining studies point towards later cohorts showing little improvement after socio-demographic changes are taken into account [44, 45] or worsening health, including more hearing impairment and worsening levels of objectively measured performance, peak flow and cognition . In the only previous study examining cohort differences in the health of older people in the UK , expansion of self-reported ill-health was evident although ADL disability appeared to have improved. As for self-reported information on diseases, increases in disability over time could be due to reductions in the stigma attached to being disabled and therefore later cohorts being more ready to report difficulties with daily life activities.
Although our study is from a rural area in East England, with a predominately white population, and a larger than average life expectancy compared with England and Wales, a strength is that the population is stable. Both cohorts had more than 70% of those interviewed resident in the area for more than 20 years and almost 10% who had been resident for 5 years or less, the new immigrants being broadly comparable in self-rated health, educational level, cognitive function, and level of disability albeit a somewhat higher proportion of new arrivals were classified as social classes 1 & 2 in 1996/7 compared with 1991/2. Comparisons of healthy life expectancy found significant differences between the five centres included in the original MRC CFAS study. However, the prevalence of functional and cognitive impairment were similar compared with the total across all five centres. Furthermore, inclusion of the total population of community-dwelling and institutional residents is a further strength of our study compared with most studies of older people.
The need to determine whether we are living longer healthier lives is imperative for all countries to plan for appropriate levels of health and social care for our expanding older population. There are therefore an increasing numbers of reports in the international literature of cohort or pseudo-cohort studies to answer this important question. That findings are mixed is not unsurprising  and may be due in part to differences in birth cohorts, diseases and conditions, severity levels of disability considered, whether objective or subjective measures are used and, for self-rated health, changing expectations. Improvements in the environment and availability of assistive devices and technological aids may also be partly responsible for disability levels remaining constant in the presence of increased disabling disease. Furthermore many studies only cover the population living in the community and some countries, particularly the UK, have seen considerable changes in the delivery of long-term care over the last decade.
The cohorts in our study were born between the two World Wars and are therefore amongst the youngest to be studied to date. Although many of the cohort differences found are not large, in the majority of diseases and conditions, change is in the same direction with increased prevalence of diseases and trends of worsening functioning and disability at milder levels. The lack of evidence of any marked improvement in population health at these ages, casts doubt over the more optimistic scenarios that have been promulgated for future development of health and health services in the UK  and adds further support to the hypothesis of expansion of morbidity in the older UK population. It remains to be seen how far trends towards worse self-reported health are attributable to increased surveillance and earlier diagnosis, increased survival with disease, or to cohort differences in the underlying disease-disability processes. Improved population-based databases, linking self-report and objective measures of health and function, and including those in long-term care are required, to understand better these trends and inform appropriate health service and policy responses.