North-south thing - in Spain the north is more an industrial/agricultural mix, south is more agricultural/tourism mix. Both areas enjoy good weather, high sunlight levels, etc, though temperatures are higher in the south overall as a southern european country the winters are shorter than northern europe. Inland is in general less populated, and south as area with high tourism has high level of transitory population, with both northern-european expatriates, and tourist industry populations fluctuating throughout the year, with many of the latter returning to their homes further north in the country for the off-season winter months.

It would be interesting to have data for France which has a more general spread of population, but similar occupational conditions, but further north.

Something which may be of interest is that both countries have Mediterranean and Atlantic coastlines, affecting diet, environment, agriculture etc similarly. If both countries followed a similar pattern of north-south incidence of PD, some inference may be possible.