We can always do with good news

 2020 has so far mostly specialized in startling, unsettling, and/or bad news.  Thank goodness for some rays of sunshine.  From Twenty-seven-year time trends in dementia incidences in Europe and the United States by Frank J. Wolters, et al.  From the Abstract:

Results Of 49,202 individuals, 4,253 (8.6%) developed dementia. The incidence rate of dementia increased with age, similarly for women and men, ranging from about 4 per 1,000 person-years in individuals aged 65–69 years to 65 per 1,000 person-years for those aged 85–89 years. The incidence rate of dementia declined by 13% per calendar decade (95% confidence interval [CI], 7%–19%), consistently across studies, and somewhat more pronouncedly in men than in women (24% [95% CI 14%–32%] vs 8% [0%–15%]).

Conclusion The incidence rate of dementia in Europe and North America has declined by 13% per decade over the past 25 years, consistently across studies. Incidence is similar for men and women, although declines were somewhat more profound in men. These observations call for sustained efforts to finding the causes for this decline, as well as determining their validity in geographically and ethnically diverse populations.

Good news but for unknown reasons.  I'll take it.  I have long wondered whether there might be some toxicity cohort effects.  As an example, I would speculate that young children growing up any time from 1900 to 1960 probably had childhood exposures to substances we now ban but whose effects might not show up until decades into adulthood.  Similar from 1960 to circa 1985 when we got pretty serious about cleaning up the environment but were still dealing with residual embedded exposures.  From 1985 on, I would expect, most children of any income level are encountering toxins from the built environment at far reduced levels than in the past.  

I am always on the lookout for changes among the older aged which might possibly be related to this weak hypothesis.  Might this be an instance?  Given the absence of any other strong hypothesis, perhaps.