Objective The oldest old are the fastest growing segment of the US population, and accurate estimates of dementia incidence in this group are crucial for healthcare planning. Although dementia incidence doubles every 5 years from ages 65 to 90 years, it is unknown if this exponential increase continues past age 90 years. Here, we estimate age- and sex-specific incidence rates of all-cause dementia in people aged 90 years and older, including estimates for centenarians. Methods Participants are from The 90+ Study, a population-based longitudinal study of aging and dementia. Three hundred thirty nondemented participants aged 90 years and older at baseline were followed between January 2003 and December 2007. Age- and sex-specific incidence rates of all-cause dementia were estimated by person-years analysis. Results The overall incidence rate of all-cause dementia was 18.2% (95% confidence interval [CI], 15.3-21.5) per year and was similar for men and women (risk ratio, 0.94; 95% CI, 0.65–1.37). Rates increased exponentially with age from 12.7% per year in the 90–94-year age group, to 21.2% per year in the 95–99-year age group, to 40.7% per year in the 100+-year age group. The doubling time based on a Poisson regression was 5.5 years. Interpretation Incidence of all-cause dementia is very high in people aged 90 years and older and continues to increase exponentially with age in both men and women. Projections of the number of people with dementia should incorporate this continuing increase of dementia incidence after age 90 years. Our results foretell the growing public health burden of dementia in an increasingly aging population.

SummaryBackgroundMenarche and menopause mark the onset and cessation, respectively, of ovarian activity associated with reproduction, and affect breast cancer risk. Our aim was to assess the strengths of their effects and determine whether they depend on characteristics of the tumours or the affected women.MethodsIndividual data from 117 epidemiological studies, including 118 964 women with invasive breast cancer and 306 091 without the disease, none of whom had used menopausal hormone therapy, were included in the analyses. We calculated adjusted relative risks (RRs) associated with menarche and menopause for breast cancer overall, and by tumour histology and by oestrogen receptor expression.FindingsBreast cancer risk increased by a factor of 1·050 (95% CI 1·044–1·057; p<0·0001) for every year younger at menarche, and independently by a smaller amount (1·029, 1·025–1·032; p<0·0001), for every year older at menopause. Premenopausal women had a greater risk of breast cancer than postmenopausal women of an identical age (RR at age 45–54 years 1·43, 1·33–1·52, p<0·001). All three of these associations were attenuated by increasing adiposity among postmenopausal women, but did not vary materially by women's year of birth, ethnic origin, childbearing history, smoking, alcohol consumption, or hormonal contraceptive use. All three associations were stronger for lobular than for ductal tumours (p<0·006 for each comparison). The effect of menopause in women of an identical age and trends by age at menopause were stronger for oestrogen receptor-positive disease than for oestrogen receptor-negative disease (p<0·01 for both comparisons).InterpretationThe effects of menarche and menopause on breast cancer risk might not be acting merely by lengthening women's total number of reproductive years. Endogenous ovarian hormones are more relevant for oestrogen receptor-positive disease than for oestrogen receptor-negative disease and for lobular than for ductal tumours.FundingCancer Research UK.

This study provides strong evidence that the addition of a progestin to HRT enhances markedly the risk of breast cancer relative to estrogen use alone. These findings have important implications for the risk-benefit equation for HRT in women using CHRT.

The authors explored the possibility that estrogen loss associated with menopause may contribute to the development of Alzheimer's disease by using a case-control study nested within a prospective cohort study. The Leisure World Cohort includes 8,877 female residents of Leisure World Laguna Hills, a retirement community in southern California, who were first mailed a health survey in 1981. From the 2,529 female cohort members who died between 1981 and 1992, the authors identified 138 with Alzheimer's disease or other dementia diagnoses likely to represent Alzheimer's disease (senile dementia, dementia, or senility) mentioned on the death certificate. Four controls were individually matched by birth date (+/- 1 year) and death date (+1 year) to each case. The risk of Alzheimer's disease and related dementia was less in estrogen users relative to nonusers (odds ratio = 0.69, 95 percent confidence interval 0.46-1.03). The risk decreased significantly with increasing estrogen dose and with increasing duration of estrogen use. Risk was also associated with variables related to endogenous estrogen levels; it increased with increasing age at menarche and (although not statistically significant) decreased with increasing weight. This study suggests that the increased incidence of Alzheimer's disease in older women may be due to estrogen deficiency and that estrogen replacement therapy may be useful for preventing or delaying the onset of this dementia.