Isaacs's lifetime work in old-age medicine began in 1948 when he was appointed house physician to the late Noah Morris, Professor of Materia Medica and Therapeutics at Glasgow University. Morris took beds not in the traditional voluntary teaching hospital but rather in a vast municipal hospital at Stobhill. Many of the patients were those unacceptable in the voluntary hospitals of the time, elderly people with chronic diseases. Morris died prematurely but his legacy - the challenge of long-term disabling illness - was taken up by his successor Stanley Alstead and his colleague Ferguson Anderson. Into this unfashionable field of medicine Bernard Isaacs entered with infectious enthusiasm.
Following National Service in Malaya from 1949 to 1951 and training in general medicine, Isaacs entered the emerging speciality of geriatrics of which he was to become a national leader. He worked first of all in the former Glasgow workhouse Forest Hall, and then in the Glasgow Royal Infirmary - though, as was the habit of the time, his department was not actually in the Infirmary but in an associated municipal hospital.
Here he developed an exemplary department and directed his incisive brain to analysing the problems of long-term illness in a growing elderly population. His first book, Survival of the Unfittest (1972), described the plight of the old and the disadvantaged in the East End of Glasgow. In it, he analysed the various reasons for admission to geriatric wards: therapeutic option (expecting rapid recovery); medical urgency (needing hospital treatment); basic care (unfit to provide food, warmth, cleanliness and safety for themselves); or relief of strain on relatives. He also characterised the principal symptoms of disparate medical and social causes of breakdown among his patients as the "Geriatric Giants": incontinence, immobility, instability (falls) and intellectual impairment.
In 1975 Isaacs was appointed to the newly established Charles Heywood Chair of Geriatric Medicine at Birmingham University. There he established a gait laboratory which extended knowledge on balance and falls in old age. It was characteristic of him to set up lectures for the staff, given by patients and their relatives. His postgraduate teaching programme included "The Great Incontinence Road Show", a serious approach to a neglected problem.
Another important innovation was the creation of the Birmingham University Centre for Applied Gerontology to promote awareness among architects, designers and service producers of the different needs of elderly people. He formed a consumer group - The Thousand Elders - to assist in market research and product evaluation, and also created the Owl Mark for products endorsed by the centre. Isaacs's last book, The Challenge of Geriatric Medicine (1992), distilled the wisdom and practical knowledge from his life's work with the wit and incisive comment of which he was a master.
Bernard Isaacs was a friendly and stimulating companion and his colleagues were delighted when he was appointed CBE in 1989. His life was grounded on his Jewish faith, strengthened by his marriage to Dorothy Berman, and he took great joy in retiring to Israel.
Bernard Isaacs, physician: born Glasgow 20 July 1924; Charles Heywood Professor of Geriatric Medicine, Birmingham University 1974-89; CBE 1989; married 1957 Dorothy Berman (four sons); died Jerusalem 24 March 1995.